I've Colette my self and I'm also a new player. My advice is to watch your triggers and don’t for get to use them (her defense trigger is very useful), also make sure to reactivate her every turn and get her to create soul stones (in the early turns) and doves (the rest of the time). Also invest in some mechanical doves (cost little) and coryphées (great for speed) to your crew. The schemes that are best to pull off are ones involving movement such as Sabotage, Power Ritual, etc. Pukll these off using Cas and your coryphées speed to get them done.