It depends on your standard of play and your willingness to re-deposit if you go broke. If you are in a position to reload another $50 without much trouble, i'd recommend playing the low stakes SnG's with 25 buy in's, meaning you could play $2 now if you wanted. Higher stakes require slightly tighter limits, i'd say 40-50 buy ins for $10 for example, so $500.
Cash games are different, it depends if you buy in for the max, min, or somewhere in-between. I wouldn't be too strict at micro levels though, just keep your game tight and leave the table UP!
Think i'd rather take a risk at 25 SnG buy ins just to avoid the $1 games. Its the same standard, so only a very slightly higher risk, but for double the reward! The only exception would be the $1 45 man SnG's, they give you some great experience for the smaller MTT's for cheap.
If your playing on FT like you mention, remember that you pay the same rake in $1 games as $2 games (.25). It only steps up in higher levels.