If you're playing SnG, it should be 45 or 90 person. PokerSars and FTP ran these that loaded rather quickly in the day (sure miss those days). Those cashes would build up fast. Cash tables can run up the bankroll fast as well.
DONs, SNGs and Heads-ups have the fewest variance, therefore they are the best to build up a bankroll, when you do some proper bankroll management.
MTTs are the worst for this, because of their big variance.
I am very good at playing Spin and Go, some say that it is the variance and another that is lucky I think everything depends on how you develop, and I have also tried to grow my bankroll with sit and go but it takes more time .
If all you care about is speed, then get in the highest cash game you can play at with a 100% buy-in. I've gone from 50$ to $1000 once or twice in a matter an hour or two by "levelling" up.
However, this is absolutely NOT the way to be a winning poker player. This is HORRID bankroll management, which happens to be a major problem of mine.
According to my experience, I have no quick way to increase my bankroll. But I have a quick way to lose the whole bankroll - it's Spin&Go or hyper-turbo knockout tournaments.