You'll win soon enough to increase it, and keep on increasing it. Your cash in hand will always be sufficient to cope with the few losses you'll suffer. Oooh, half a dozen at the most; certainly not twenty or thirty on the bounce.
Should Fate actually dare to treat you so badly, simply replenish the bankroll, make a loan to it – you know, just for the short while that you're in the red. It won't be a question of throwing more money at the game; you'll take the loan back when the winning times return.
As they surely must.