This is a various question to be and could have different solutions.
What it seems like is that every time you line up a several Pokemon, the Pokemon you line up with get that exp. It seems to me like in order to level up, you should try to line up that Pokemon many many times. I don't think the level has anything to do with, but some levels might make it easier to line up, giving you many exp. I took me approximately 3-5 levels to move a Pokemon from level 1 to level 2. But, it will obviously increase and get harder overtime. I think you should enjoy the game and gradually continue lining up with various Pokemon, therefore they would grow together and faster.
Hopefully I've helped. Anymore question could be answered. :)