As requested, here is my attempt at coming up with a "formula" for how I play sprites. It's more or less the same every game, although Omniscient should make the games slightly more varied due to having more colours at my disposal. Bear with me if it looks rushed, Seravy requested that I make it available in time for the start of his next game. Seravy, do you want to upload the game you start so we can all try it for comparison? Note that after Conjurer is weakened I recommend swapping it for another Nature book (taking Web) instead.
1) Early magic priorities
a. Heavenly Light on any city that doesn't have it.
b. Earth Lore (centered on your capital unless there is a lot of ocean).
c. If you have one or more useful targets, summon enough sprites to take out those targets.
d. When you're running low on targets, cast Earth Lore again to locate more.
e. Run max mana until you can fuel your casting skill fully with it, then start prioritizing skill.
f. Do crash spending on research whenever something really important is available (especially useful combat spells and Summoning Circle) and you feel you can afford it (typically after you have a node or 2 cities with Shrine + Heavenly Light).
2) Strategic priorities
a. Neutral cities with zero threats are top priority.
b. Sorcery nodes with zero threats are almost as high priority, especially if there aren't nagas.
c. Neutral cities with small threats are also very high priority (Web is a life saver here).
d. Lairs without threats should be put in your strategic plan whenever they fit, make sure to optimize your movement points.
3) Economic priorities
a. Use enough Alchemy early on that you can use all your casting skill each turn, stop using Alchemy when you've located mana treasure or your power is high enough to fuel your spells with your power base.
b. Settlers are very high priority, I recommend spamming settlers non-stop until all decent spots within 15 tiles or so are filled. Don't worry too much about defenses (change this priority a bit depending on how close your enemies are).
c. New cities should rush builder's hall => housing => sawmill => shrine (high pop sites) or sawmill => shrine (high production sites). Use spearmen for garrison as needed.
d. Once you've expanded decently and shrines are up, start putting up marketplace + granary + farmer's market + forester's guild in roughly that order (my analysis of those buildings isn't complete yet).
e. Run max taxes at all times, supplement with spearmen as needed.
f. Selling your smithy is recommended.
4) After the early game
Once you have a few cities with Heavenly Light and 1-2 nodes, you have a very strong power base. Start building bigger sprite stacks so you can take out the bigger targets, and make sure to formulate a strategic conquest plan that lets you minimize wasted movement. Give high prioritiy to Earth Lore, and try to take as many neutral cities as possible.
Depending on how close your nearest rival is, you may want to do an early strike (1404 or sooner). War Bears, skeletons or hell hounds can help greatly in assisting your main sprite stack. Find his capital quickly and send a unit of sprites to see what his defenses are comprised of. Typically there'll be nagas if he's sorcery, ghouls if he's death, sprites if he's nature and hell hounds if he's chaos. Only sprites and ghouls are a threat to you. If he doesn't have either, go for the throat as fast as possible (keep taking out other targets while you build a stack of 9 sprites and maybe a secondary stack to soften him up if necessary). It's important that the sprite stack can finish the kill, otherwise fortress lightning will tear you apart.
If you can't take out his capital, consider taking out all his outposts or let them grow to size 1 if you can commit enough troops. Your casting skill should be very high at this point, and it shouldn't take you long to conjure enough troops to go on the offensive. Don't worry too much about defenses, just make sure you have early warning of his movements.
Past 1405 or so, play it as you normally would. You're off to a powerful start unless you've been very unlucky or messed up and lost your sprites, and your economic base should be phenomenal with all the boosts each city gets. Try to consolidate your possessions and start focusing more on defense, then find your next target and take out another AI by 1408 or so. With two Arcanus wizards down you'll have a very large empire with very productive cities. Use whatever spells come your way and keep building large armies so you're ready to go on the offensive when you see a weak spot. Scout out the entire plane with Earth Lore and keep taking out all the easy nodes, you should have 5-6 in no time. Put a single unit in each for defense, don't overdo it.
You should be able to pick up a few heroes from lairs and a handful of items for them. Make the most of them, include them in your lair stomping stacks so they can pick up easy experience.
By the time you're ready to take out your third AI, chances are he'll be fairly formidable and require multiple fortress strikes to take out. Scout out his cities thoroughly so you know what defenses to plan for, build a number of medium strength stacks that can take out medium strength cities with minimal casualties. You should be able to take out 6-8 cities per fortress strike for maximum efficiency.
5) Game setup
This strategy is very reliable for almost any setup, even more so now that we have Omniscient. I like playing with High Power and Huge land, but it doesn't make that much difference. Play on Impossible, you should have better than 50% chances of winning.
6) Wizard setup
3x Nature (Sprites + Earth Lore)
2x Life (Heavenly Light)
1x Chaos
1x Death
2 Spellweaver
1 Omniscient
1 Conjurer
1 Cult Leader
I'm not 100% sure how the power bonuses compound and round, but this will get you 5 power per shrine, 8 power per Heavenly Light and 10 power per parthenon. Shrine + Parthenon Cathedral + Heavenly Light = 38 power per city.
I'm fairly certain this is the strongest setup for a sprite strategy. Note that you don't win with sprites, you just achieve a powerful start that will allow you to do anything you want a little while later. There isn't much room for change either, everything above is needed. When Conjurer is weakened I'll probably swap it for another Nature book and start with Web.
Multiple races are viable for this strategy. You will want to spam your starting race in many locations, so having access to all 3 religious buildings is a must. That leaves Halflings, High Elves, High Men, Nomads and Orcs. Of those, Halflings and High Elves have advantages that help you right out the gate: Halflings have extra food and research, High Elves have extra power. Those are my 2 favourite races for this strategy right now. Nomads are also good, letting you supplement your creatures with the excellent horsebowman unit very quickly and upgrading to the incredible ranger unit later on. High Men seem unimpressive to me, their advantages come too late to be of substantial assistance and they suffer an unrest penalty. Orcs are equally unimpressive, they grow fast but they don't have any great units.
1) Early magic priorities
a. Heavenly Light on any city that doesn't have it.
b. Earth Lore (centered on your capital unless there is a lot of ocean).
c. If you have one or more useful targets, summon enough sprites to take out those targets.
d. When you're running low on targets, cast Earth Lore again to locate more.
e. Run max mana until you can fuel your casting skill fully with it, then start prioritizing skill.
f. Do crash spending on research whenever something really important is available (especially useful combat spells and Summoning Circle) and you feel you can afford it (typically after you have a node or 2 cities with Shrine + Heavenly Light).
2) Strategic priorities
a. Neutral cities with zero threats are top priority.
b. Sorcery nodes with zero threats are almost as high priority, especially if there aren't nagas.
c. Neutral cities with small threats are also very high priority (Web is a life saver here).
d. Lairs without threats should be put in your strategic plan whenever they fit, make sure to optimize your movement points.
3) Economic priorities
a. Use enough Alchemy early on that you can use all your casting skill each turn, stop using Alchemy when you've located mana treasure or your power is high enough to fuel your spells with your power base.
b. Settlers are very high priority, I recommend spamming settlers non-stop until all decent spots within 15 tiles or so are filled. Don't worry too much about defenses (change this priority a bit depending on how close your enemies are).
c. New cities should rush builder's hall => housing => sawmill => shrine (high pop sites) or sawmill => shrine (high production sites). Use spearmen for garrison as needed.
d. Once you've expanded decently and shrines are up, start putting up marketplace + granary + farmer's market + forester's guild in roughly that order (my analysis of those buildings isn't complete yet).
e. Run max taxes at all times, supplement with spearmen as needed.
f. Selling your smithy is recommended.
4) After the early game
Once you have a few cities with Heavenly Light and 1-2 nodes, you have a very strong power base. Start building bigger sprite stacks so you can take out the bigger targets, and make sure to formulate a strategic conquest plan that lets you minimize wasted movement. Give high prioritiy to Earth Lore, and try to take as many neutral cities as possible.
Depending on how close your nearest rival is, you may want to do an early strike (1404 or sooner). War Bears, skeletons or hell hounds can help greatly in assisting your main sprite stack. Find his capital quickly and send a unit of sprites to see what his defenses are comprised of. Typically there'll be nagas if he's sorcery, ghouls if he's death, sprites if he's nature and hell hounds if he's chaos. Only sprites and ghouls are a threat to you. If he doesn't have either, go for the throat as fast as possible (keep taking out other targets while you build a stack of 9 sprites and maybe a secondary stack to soften him up if necessary). It's important that the sprite stack can finish the kill, otherwise fortress lightning will tear you apart.
If you can't take out his capital, consider taking out all his outposts or let them grow to size 1 if you can commit enough troops. Your casting skill should be very high at this point, and it shouldn't take you long to conjure enough troops to go on the offensive. Don't worry too much about defenses, just make sure you have early warning of his movements.
Past 1405 or so, play it as you normally would. You're off to a powerful start unless you've been very unlucky or messed up and lost your sprites, and your economic base should be phenomenal with all the boosts each city gets. Try to consolidate your possessions and start focusing more on defense, then find your next target and take out another AI by 1408 or so. With two Arcanus wizards down you'll have a very large empire with very productive cities. Use whatever spells come your way and keep building large armies so you're ready to go on the offensive when you see a weak spot. Scout out the entire plane with Earth Lore and keep taking out all the easy nodes, you should have 5-6 in no time. Put a single unit in each for defense, don't overdo it.
You should be able to pick up a few heroes from lairs and a handful of items for them. Make the most of them, include them in your lair stomping stacks so they can pick up easy experience.
By the time you're ready to take out your third AI, chances are he'll be fairly formidable and require multiple fortress strikes to take out. Scout out his cities thoroughly so you know what defenses to plan for, build a number of medium strength stacks that can take out medium strength cities with minimal casualties. You should be able to take out 6-8 cities per fortress strike for maximum efficiency.
5) Game setup
This strategy is very reliable for almost any setup, even more so now that we have Omniscient. I like playing with High Power and Huge land, but it doesn't make that much difference. Play on Impossible, you should have better than 50% chances of winning.
6) Wizard setup
3x Nature (Sprites + Earth Lore)
2x Life (Heavenly Light)
1x Chaos
1x Death
2 Spellweaver
1 Omniscient
1 Conjurer
1 Cult Leader
I'm not 100% sure how the power bonuses compound and round, but this will get you 5 power per shrine, 8 power per Heavenly Light and 10 power per parthenon. Shrine + Parthenon Cathedral + Heavenly Light = 38 power per city.
I'm fairly certain this is the strongest setup for a sprite strategy. Note that you don't win with sprites, you just achieve a powerful start that will allow you to do anything you want a little while later. There isn't much room for change either, everything above is needed. When Conjurer is weakened I'll probably swap it for another Nature book and start with Web.
Multiple races are viable for this strategy. You will want to spam your starting race in many locations, so having access to all 3 religious buildings is a must. That leaves Halflings, High Elves, High Men, Nomads and Orcs. Of those, Halflings and High Elves have advantages that help you right out the gate: Halflings have extra food and research, High Elves have extra power. Those are my 2 favourite races for this strategy right now. Nomads are also good, letting you supplement your creatures with the excellent horsebowman unit very quickly and upgrading to the incredible ranger unit later on. High Men seem unimpressive to me, their advantages come too late to be of substantial assistance and they suffer an unrest penalty. Orcs are equally unimpressive, they grow fast but they don't have any great units.