This is one of the most common questions, and often depends on the individual. It is possible to start small and build up, and starting with software is a big help here: the training mode setting will ensure that no actual cash is lost while you are learning. What’s more, starting small is usually the advice most pros will give you, because at the very beginning, no matter how good you think you are, you are still an amateur at best. All in all, start at £100 or £200 at most. If not that, then consider how much money you’re willing to lose, and start with that amount.