I am sorry but I don’t think you will find what you are looking for here on the forums. I hope you do but just like with LFG the chances are slim to find such a player. There was this guy though: An update on my project who maybe would be interested in helping you.
I wonder how you see this as different as a boost though? Paying a coach vs playing with a better player who teaches you how to play?
My suggestion would be to play with your PvE friends if any of them are into arenas or try to socialize yourself with someone in a random bg or similar and start playing with them from the same level.
Best of luck!