It's been a couple of months, when Im asked to develop a carrousel or something kind of 'extra' I tend to create a new folder and develop it from scratch as long as it's something kind of basic with not a lot of features; why? because developing something complex with a lot of features from scratch would take a lot of time, will have bugs that then will have to be taken care of... in those cases I always use a plugin. But it's always good to create your own stuff experimenting yourself.