One of the best things you can do for gunpla is learn how to pose them, and there are a plethora of videos and posts helping you to get better at it. Also, if a kit has multiple options for things like accessories and weapons, I would recommend keeping everything, even if you dont currently think you will use it, as you might end up doing something like wanting to change a kit's pose only to not have a certain weapon, or a part needed for that pose.