these are things to do:

in primeval age:
use more clubmen than slingers at start, then upgrade your primitve turret. Dino riders will help you to gain experience. Sometimes is good to use volcano power.

in medieval:
quick use footmen to push back enemy lines. Crossbowmen help if you dont have too soldiers of enemy to fight. Then add new turret platform and replace one old for new. Knights are usable only at the end of age

in post-medieval:
dueleros are cheap and weak,musketeers expensive and strong: so you may choose. Dont use canons : too expensive, too slow!

in modern age:
light infantry is perfect skirmish unit, then you may use snipers to big attack. Tanks are strong but unhelpful. Dont forget to use bombs.

in atomic age:
god swordsmen are veery good to final attack on base. Helpful are also robots armed with rifles, good against machines. And total bomb is super soldier who destroy all what is between him and base.

Thatz all ..enjoy!