trouble with this, in my experience is i found that no one wants to boost, as its frustrating, boring and you could just be having a laugh playing something else. If i had another xbox believe me id have taken the easy option in this rare case and boosted myself (as per the above solution) because this will annoy you, no end.
If you want it legit, or simply are forced to do obtain it legit then you can expect this:
I played 265 battles, winning 198 of them. this took about 30 hours.
around 50!! people quit on me, severly slowing down the process of levelling up. (usually id get 4 or 5 wins in a row, before someone quit.) it is the quitting that is soul destroying, if only they didnt, then the win streak bonus of x10 (100 dj points) for each mix speeds things up drastically. I never saw past a x7 so i wouldnt know.
im an expert player but played mostly on medium, this is because i would usually win, and fc the mix (easilly) so id end up with around 30djp per battle.
go for 1 mix battles. try and do 10, to get the 10 mixes in a row, prob endup 12 with 2 people quitting. you get 100 djp or the 10 mixes so its important.
Avoid the checkpoint and dj battles, i found them incredably frustrating and would usually result in a loss the occassional time i played them. (seemed very random to me)
avoid very low players, especially lvl 1 etc as they nearly always quit (lack of skill, or not understanding the rules of the game mode)
i often did a couple of 3 mix battles, purpously letting the other player win the first or 2nd mix (not use any star power, or effects special scratching, whilst maintaing an fc) and then id win the last, winning 2 -1 whilst fc ing each mix usually gave me 90+ djp. as pointed out in other guides you need 12,740. its alot! stick with it, do a couple hours at a time, 10 1 mix battles each time and with fcs if you can and it will be yours! also dont quit your self, as you dont keep your win streak etc and you ll be just as bad as the others out there. (iv never given such bad feedback to soooo many people lol)
took me just under two weeks. on the plus side i did enjoy playing it and am proud i got this legit ;)