IMHO, the best Sport to bet it on is the Sport where you're interested into and have enough knowledge about the game, the association, the players, and even the coaches. These knowledge maybe enough to let you analyze match ups and mitigate the possibility of lossing even betting against the odds.
NBA has been a good betting for Sports for me, simply because I can bet like 3-5 times everyday as there are usually 8 games and 16 teams are playing everyday.
So, when you lose from the current match, then maybe you'll win from the next one. Or win them all, worse lose them all. That's the nature of gambling anyway.