It depends on what kind of game and denomination I'm playing. I like to play reel slots with bonuses like Wheel of Fortune and Top Dollar machines. But for any general 3 Reel slots, I would only invest about 50 times the max bet. So when I play the $5 WoF or Top Dollar, I would invest $500 max. I would cash out when I have doubled my bankroll at that machine. If I am above my goal, I will usually try to push it to as far as it can go and quitting when I've doubled/tripled my bankroll. Personally, I found more success at $5 and higher machines. So on any given trip, I would bring about $2500, just to have the luxury to play multiple machines if one isn't working out.