Kage, thanks a lot for all this advice. I'll try to focus on it, although I like that I've already been doing a lot of it. One slight difference, though, is I try fun stuff on P:M instead of against my friends. The fun stuff I try is crazy jump off edge KOs, just to see if they'll actually reach, and working out little tricks. I'm still not consistent enough at shield drop Uair, though, but I doubt I'll need it that often. My shield drop is fine, and my platform drop Uair is fine, but I have a bit of trouble combining them. In general, I'm trying to push myself to move even faster than I currently do. I'm also working on my OoS options, since I forget to use them a lot, and just roll or grab. Shuffled aerials, wavedashes, and shield drops (if I'm on a platform) are other things I should be trying.
Against friends I build up pocket characters. Since my friends aren't good enough to give me actual matchup experience, I'm getting my pocket characters to the point where I can learn matchup experience from myself. For example, a couple weeks ago I did my first techchase and combo with Falcon. Once I got the hang of doing that with Falcon, I worked out how to counter it with Ganon.