While general rule of 50-100 buy-ins is correct for sitngoes for online poker players who want to try to take poker seriously, I also think that playing style takes a role too.
If you're a loose-aggressive player, you will need more buy-ins than what most people recommend because you will be facing way more variance.
If you're conservative, tight-aggressive player, then you will be able to manage with common brm rules.
I personally like to have over 100 because I play very loose and when I am on downswing, I can lose a lot because I've had over 30 buy-ins of downswings at $2 sngs but when running hot, I've bumped up my bankroll so quickly that I blazed through $2 sngs by making over $300 and immediately moved upto $5 sngs before Black Friday occurred.
Another thing you need to factor is tilt control. How good is your tilt control. No matter how good player you are, if you tilt off easily, or if you are a type of player who still play under tilted mindset, then you will go broke easily if you use aggressive brm.
Bottomline, loose-aggressive players will need conservative bankroll management(50-100 buy-ins, even more).
Tight-aggressive conservative players can manage with aggressive bankroll management(20-30 buy-ins).