A while ago I ran a sci-fi magic RP where you could pick a power, like acid where metals you touched melted, or climate where you can control the temperature, or even healing where you can reverse small wounds. It all seemed rather generic until I added a crystal charging ability where charged crystals could be used to amplify the effects of one's abilities and even modify them. This in turn crested an economy where I can create crystal rarity, dangers of overcharged crystals exploding, and even side effects for prolonged use or simplifying too much power. 

It added a layer and allowed me to create a motive for people, but also a history and depth. I could have characters almost self govern their abilities because I could limit their "mana" restoration amount as well as their ability strength. It also doesn't have to be too complicated. You could run the typical common/uncommon/rare system or even a scale that has strength levels that decrease the longer the an ability is used, ie: short and potent or long and weak.