In my limited experience, it depends on the buy-in and time of day. Playing on pokerstars
at 10am CET on a weekday, there will be regs multitabling at $3.50/$7.00 hyper turbos, so you can see a solid game. Evenings/weekends there can even be random gamblers at $60 in the same format.
I was more comfortable at the beginning playing good players at higher stakes tables with a LAG strategy and learning the game; often the lowest stakes can be like play money and not a useful learning tool.
If you have the time or cash, playing higher stakes can be useful to experience games where people follow the rules and if you then drop back to $3.50/$7.00 tables, these are much easier to beat as suddenly the fishies shine from a mile off.
I am far from an expert, this is just my experience of sngs - I still had a 33% ITM on 6-seater $1.50 games before I moved up.