If you are a very sound Omaha/8 player, you can play with a 200 big bet bankroll. If you had started with 300 big bets and are down 50, you have only lost roughly 17% of your bankroll.
However, if you start with only 100 times the big bet, if you are down 50 big bets you have lost 50% of your bankroll. 50 times the big bet is a common downswing, even for professional poker players, and nothing to become too concerned about if you are still playing well. This is a psychological hurdle but when reduced to facts it makes sense. I have played at levels that I had much less than 300 times the big bet in bankroll and it sometimes hurts my play. I play much better when I have this cushion. My recommendation, particularly for holdem, is to start with 300 times the big bet. I have seen poker bankroll size suggestions ranging from 200 times the big bet at the level you are playing at ($800 at 2/4) to 300 times the big bet ($1200 at 2/4).
