Obviously, the less tables and players involved, the less variance there is so the easier it is to finish in the money in a single table SNG.
And it is a grind to build a decent bankroll from SNGs. A good player can expect a ROI of 15-20%. That means in order to win $100, you have play in $500 worth of SNGs, or 50 $11 SNGs or 100 $5 SNGs.
Make sure you have a minimum of 30 buy-ins for the level you are playing because variance is a b***** and 5,6 or 10 swings without cashing happen, to even the best.
My current streak is not cashing in 8 straight at the moment (super tilt) and my ROI over 1500+ games is 28%.