Mages are the most powerful fighters, but are rare. They can cast magic spells to help and harm. The repertoire of spells is very limited as are their ranges. But, magic has its own limits. Only so many points of spells may be cast in a given time period.
Magic items have their own uses.
Some provide improved armor or fighting ability, some eliminate the possibility of a unit breaking. Others provide magical attacks, and so on. But, units may only carry as many items as they have experience levels. Those used to games like Warcraft will find that the control interface is radically different. Units move as units, having to turn in formation, rotate to fire their weapons, etc.