Hmmm, ROB on rainbow ride, I m going to ignore chracter specifics and jsut talk aobut how to play on rainbow ride in gerenal, and how I play on that stage.
1.Learn to assert your ground: asserting your ground is important, because most people will try to get the lower ground when playing smash, but with rainbow ride, its better to learn how to attack while manipulating your opponent, you do this my keeping youself on a certain platform, best example for me is the carpets, people will try undernith, but just reel the oppoent in, because it is a test of camping and waiting.
2. Learn good aerial game: learn the priority, range, timing of your aerials, this is basic, because you need to keep moving. not much to say here, its rpetty simple.
3 . Should you have bad aerial game, find a better alternative, this is made more aparant with one of my chracters, Donkey Kong, since his down air is while powerful, is predictable, no ranged hitbox to mindgame. and has prety harsh landing lag should you mess up, so heres what I do with him,I will utalise running away and either chargin a donkey punch, space and super armor b up, etc.
All and all, playing rainbow ride is pretty much learning to watch our opponent, watching your stage, and knowing when to change ground and assert it, this is knowlage when you remember your attacks, try not to be too afraid either. just test what works, I ue Olimar on rainbow ride, and i have not lost a single game on hat stage yet.
I hope this is ok enough, just ask me if you want me to explain, keep in mind that this is not chracter specific, but i used characters that I can use as reference as to what I can do and what I learned myself, this is all from my experiance, and not learned from anyone else.