For practice, I use FMJ (Ball) ammo in all my .223 and .308's.  Unless you are hunting, or sitting down for some serious target work, why spend more $.  For more serious uses, it depends what I'm expecting to shoot at.  I like the Nosler PT in the .223 for self defense, and what ever frangible varmint bullet shoots well in that particular gun for varmints.  In the .308, again, I like Nosler PT's, although my M1a shoots 150 grain Ballistic Tips very accurately.  In my AK, I just use cheap Russian FMJ, as it is not really a hunting gun, and will never be a target rifle.
Larry