Actually, I would say never invest more than 1/100 to 1/50 of your bankroll . When you gamble 1/10 of it, you are almost guaranteed to go broke, as even the BEST players out there will have longer than 10 games downswings...
I'm comfortable with 5% because it always stays 5%. If I have $100 and then lose a $5 buy in, then I can't play in another $5 buy in because I don't have the br for it. So 5% doesn't mean I have 20 entries at 1 level, it's more a guide to tell me what level I can play at.
I'm gonna give that bitch a freeroll, bitches love freerolls.