The game heavily favors fewer powerful units over swarms of weak units so I usually do one of two things at the beginning of the game: 1) destroy buildings and go straight to advanced units like mages/trolls/vampires or 2) go for smithy/barracks/academy to get the upgraded units asap. I only produce tier 1 units if I absolutely have to but if you make too many, you will not be able to support more powerful units. Making just 2 trolls at the beginning of the game is definitely doable and absolutely worth it. Once you start trying out armageddon mode, you will probably be most successful by going for advanced caster units, especially vampires/mages. Warlocks (koatl village) also make great units and can stun like bowmasters but do much more damage. Once you find a holy grounds, start making divine units asap and forget the weak stuff. Focus your buffs on heroes/tier 3 units and they will make you unstoppable. My best advice is simply to try all units of every faction so you can learn what works and doesn't work. There is no reason to "power game" with Warlock or you will get bored really fast.
As for spells, try to get your research up right away because spells can make or break the game. I usually reserve my mana for casting buffs on key units and try to limit my casting at the beginning of the game. Many people say summoning spells are extremely overpowered and a cheap tactic, so I never summon unless I need to. Experiment with all 8 gods and learn the strengths/weaknesses of all their spells and units. That's what makes Warlock so fun and why I have so many damn hours played. Happy gaming man!
Thanks for tha mate, i think I'll finish the game I'm playing then try doing as you say, go for the more powerful units. Either way, I'm enjoying the game so much, DLC's are getting bought tonight lol