Touch sensitive interfaces enable new interaction methods like using gesture commands. To easily memorize more than a dozen of gesture commands, it is important to be able to customize them. The classifier used to recognize drawn symbols must hence be customisable, able to learn from very few data, and evolving, able to learn and improve during its use. This work studies different supervision strategies for the online training of the evolving classifier. We compare six supervision strategies, depending on user interaction (solicitation by the system), and self-evaluation capacities (notion of reject). In particular, there is a trade-off between the number of user interactions, to supervise the online training, and the error rate of the classifier. We show in this paper that the strategy giving the best results is to learn from data validated by the user, when the confidence of the recognition is too low, and from data implicitly validated.