I advise you to listen to those who recommend playing with no more than 2% of your bankroll or 50 buy ins for 6-9 max STTs, and to have at least 100 buy ins if you plan to play 45s-180s. I use to grind STTs before Black Friday, and if you are good there is as much profit to be made as their in in cash games. It is a system. Figure out what works. You'll need to figure out when to be aggressive, when to tighten up and how chip stacks influence absolutely everything.
If this is your fist experience grinding SNGs, I recommend grinding either 6 or 9 max, whichever suits your style of play best. These are what will slowly but surely build your bankroll if you are a winning player. Begin to mix in the 45s, 90s, and 180s as you become more comfortable with the format and confident in your play.