Honestly from my personal experience, it's always smarter to have a set amount you’re okay with losing and just walk away once it’s gone also  I don’t think a reserve balance for gambling is really necessary unless you’re someone who treats it like a serious hobby or part of your lifestyle. For me it works better to set a budget like entertainment money, once that’s used up I’m done. Having a reserve might tempt you to keep chasing losses which never ends well So I would say stick to what you can afford to lose in one go and avoid the backup stash