To begin, if you're talking about pressing the opponent direction and then pressing B to turn around when you do the move, it is a thing in Melee, we just call it turnaround, or reverse. Turnaround laser is still in the game.
And as for the wavedash problems, Marth's jumpsquat (the moment right before the character jumps) is 5 frames, which is one frame faster than Falco's wavedash. If you're used to playing characters who do them incredibly fast (like Fox or Pikachu) then it's the timing you're messing up.
The biggest things I think you need to work on is finding your style as a player, and then basing your practice around that.
You should be able to tell whether you're a very aggressive or very defensive player. (or somewhere in the middle.) Do you prefer to play in an optimized way, or in a flashy stylish way?
If you're a more optimized and "frame perfect" kind of player then watch Zhu's matches, and his "SmashPractice" videos with Cactuar because they're incredibly helpful and insightful. Also watch PPMD's falco. Both of these players are very good at things like option coverage, how to continue combos and how to apply pressure without throwing out moves.
If you're a stylish flashy "gfycat" kind of player, then watching Westballz is the way to go. He's incredibly combo oriented, and is almost always on the attack. You can learn how to be a sick Falco from him, but don't expect to watch some slowed down play. Anther amazing Falco to watch for this is MaNg0's falco. (the sickest of them all.)
The other must watch Falco's are DaShizWiz, the FL legend, and Porkchops, the senpai of Falcos.
As for what you should learn, try to not waste time with things like quadruple shine out of shield, and try to learn how to play the game really well (fundamentals). Things like spacing, pressure, DI, punishes, stuff like that. If you're confident in your fundamentals then practice shield pressure with and without shines, the range of ALL of your moves (and their hitboxes), and watch videos of all of the matchups against the top 8 characters so that in pools you won't lose to matchup inexperience.
And above all, have fun!