I would like to know how I can fix the fighters to take example 15 skills from the buffer  , mages 10 and if they take more to start removing the buffs they have already taken I have to modify buffer's script or what ?

If by "the buffer" you mean "the integrated scheme buffer from L2J", you just have to add a check about how many buffs they actually got, if they got more than xx, do a return.