I'm not sure you've looked at the PvP. Calling it "PvP" is a stretch. As far as I can tell it's simply a ladder board, (based on level ups) with an eventual pay out based on how many levelups you've made, capping out at 11000 getting 150 gems, 75 keys, and 5 5d advances.
(fwiw, I'm in the 6k's, getting 50 gems, 30 keys, 3 1d advances. Next bracket is 7k, which I probably won't reach with ~1 day left this round.)
My doing well because of decorations/time spent in no way prevents somebody else from doing well.