You can always find out what topics or videos are trending by going onto YouTube and then clicking the "trending" tab just underneath the main search bar. As for your videos I would say don't worry so much about what is trending do something you enjoy - if you like doing makeup videos then do this, if you prefer fashion do those, or if you like them both why not do a channel about them both? Ultimately that's the joy of YouTube giving you the space to create a channel about anything