Best to have a bankroll-to-buyin ratio of 100:1. Also before you start playing buy-ins,
it is best if you make a win/loss bankroll plan and stick to it religiously.
Example, you want to start playing 1$ SNG's.
First BR should be no less than 100$. ( roughly, also take into account the house fee )
Second, Win/Loss plan set for 20% test run. In other words, keep track of every dollar you buy-in,
whether it wins or loses.
Once you have "played" 20% of your BR, your W/L ratio will signal if you can continue profitably,
or should consider smaller stakes.
If your overall profit ( current BR-Initial BR ) is +20%, and site allows multiple accounts
( just not playing at same time ), move a percentage of profit to second account.
( that way you have a buffer for the bad days, which happen to all of us ).
If ever you have to dip into your buffer, no more than 10% should be withdrawn per day.
No more than 50% EVER. that way you still have room to rebuild, and it won't take forever to do so.
If at anytime you lose 40% of your BR, with little to no profit, STOP.
You are outclassed, bleeding money and heading down the road to ruin. Best thing is re-evaluate
your game, rebuild the BR, and start again at lower stakes.
Good Luck at the tables and remember : digging a hole is easy, getting out of one takes some work.