Bankroll guidelines vary based on your playing style, but anyone just starting out should understand the short term luck involved with poker. Many newer players, after a good session, think that a winning player should win almost any time they sit at a table. This is simply not true, and many long term winning players win no more than 55% of the sessions they play. Because of this short-term luck factor, you must have a reasonably sized bankroll to overcome simple variance.
The general rule of thumb used to be a starting bankroll of 300 BB’s (a BB, or “big bet” is the amount of the bet needed for the turn and river. For example, at 2/4 the BIG BET would be 4 dollars, and at 15/30 the BIG BET would be 30 dollars). Downswings as big as 500-700 big bets, though rare, are certainly possible even with optimal play.
Our suggestion is to first decide why you are playing poker. If you are playing purely for recreation and the thrill of victory, play whatever limit you are comfortable with based on your financial situation and do not risk money at a table that you cannot afford to lose. If you are worried about losing the money but could replenish your bankroll if you went bust, then try to keep anywhere from 100-150BB’s in your current role. If you play poker seriously and do not want more than a 5% risk of going broke, then having 300 BB’s is ok if, and only if, you are willing to drop down in limits during a downswing. If you are playing poker for a living then you should have no less than 500BB’s AND six months of living expenses saved in a non-poker bank account.