I'm not very familiar with Gamanche novels specifically. But generally, the order could be based on the publication date. The first published one would be a good starting point, followed by subsequent releases in chronological order.
The order of Gamanche novels could also potentially be guided by the complexity of the storylines. Maybe the simpler, more introductory ones come first, gradually leading to the more complex and in - depth novels. Another factor could be the popularity of the novels among readers. If there are some that are highly recommended as entry points by the reading community, those might be the ones to start with. Without actually having read these novels or having more detailed information about them, it's difficult to give a definite order.