If you only play 5-10 SnGs a week, it could be an option to not even have a bankroll but just pay out of pocket / paychecks. But if you want to set aside a finite amount for poker, then I would recommend to spend no more than 2% of your bankroll on a STT and no more than 1% on a MTT. So maybe 1.000$ would be reasonable. 20$ is a little high to start online though, so maybe consider to start a little lower but increase volume. With a bit of practice its not to difficult to fire up a set of 4 STTs at the same time and then let the count drop, as usually you bust from some of them.
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