WARNING: doing this may spoil the game for you, but if you want tips, here ya go:
Start with a kingdom faction (easier to start), use a sovereign with organized (for extra cheese), make sure to build your capital near a tech library. Don't try expand like crazy and leave your cities practically undefended, just stick around your main city, build up your city and a few conscript (upgraded peasants with staves) just to get everyone off your back for having no military. The quickest way to getting strong units is to go straight for catapults, this takes just 4 tech in the warfare tree (Logistic -> City Defense -> Seige -> Catapult). Don't bother with building generics units until later on when you can pull out vet lord hammers squads/company. Research Production (in Civics) if you don't have a material resource nearby (and build the Great Mill), then research 4 levels in exploration adventuring tech for the resources (gold mine, 2 food source, another gold mine, ventri mines), now you are set for resources to build your military. Pump out catapult, stack them with your sovereign for faster movement, declare war on the nearest guy and smack them in the face with boulders, take all their cities, kill their sovereign. It was nice of them to build those cities for you wasn't it? Rinse, Repeat, Win.
Empire strategy is very similar (their catapults are even stronger, lol), it just has harder mats requirement (and no Great Mill) so you have to set that up.