Well first of all if you don't know how to beat the normal mode of this game you're bad at this game.
First age "caveman age"
first make a dino rider then make as many club infantry as you can becuase they are stronger then slingshot infantry
and cheaper. you should only use the volcano if there is to many enemies around. wait till you get 4000 exp.
sencond age "Medivel ages"
now make as many swordsmen as you can
then wait till for your guys to fight and save the money you get to buy a knight make as many knights as you can.wait till you get 14000 exp
thired age"Crusade"
make as many canoneers and mousquetteres as you can if needed build a turret
fourth age "modern war"
build as many tanks as you can and maybe some machine gun infantry buid some rocket launcher turrets too.
fifth age "future"
this is the last and easist age of them all just build the Ionray turret it hurts infantry lots and it shoots far and it might hit the enimies base