[@liferusher] The runes can be used to do any kind of magic, and even combine different ones to make for various effects (like freeze and electricity). However most of the runes that can be cast instantly are like caltrops from DnD, simple and memorable spells that are engrabed in the users memory. Larger spells need premade runes that need time to be prepared. More powerful spells take more time and better materials. Eg: a medium spell can be fitted onto stone or wood, but powerful ones need crystals or metal. Or they can be cast on the air if you are willing to chant and do funky dance moves for 48 hourst straight. 

Ps: Runes still need time to cast, but not that much.