Struggling to use Lucas

I’ve been using king k rool as my main in smash for the longest and I never bother using another character. I’ve recently started using Lucas and I genuinely feel like I have no skill in the game I’ve been using him none stop and I can’t seem to win any games or do damage at all. I’m getting cooked left and right. For context my gsp with King K is about 10.5mil but with Lucas it’s an astonishing 3.5mil barely. Any tips in general?