Mymlvl 16 breton battlemage started out with heavy armor was going to use conjuration to summon weapons and minions and use a little restoration. Around lvl 12 i decided to add destruction for some ranged attake but i recently bought a bound bow spell and now i cant decide between destructon or bound bow for ranged damage. Which one should i go with??

Depends on which skill you want to increase - Marksman or Destruction? You'll have to invest in one of them, otherwise the damage will be so small it's not worth it. Destruction is better for role-playing purposes, Marksman is better for late-game maximum damage.

At this point, I'd stick with your original plan and use the bound bow. Destruction works, but it does require more dedication and focus. If you've only started using Destruction at lvl 12, it will lag behind.