practice CG against level 3 against fast fallers. you can also practice some combos but keep in mind that people will DI differently. you can practice edgeguarding low recoveries from fox and falco by back throwing at the edge. they always late jump and firefox diagonally. cpus also rarely tech but it's not frequent enough to practice with. different CPUs have different tech habits. you can try to get acquainted with tech chasing a bit on reaction by finding a cpu in trainign mode or a level that will pick a few different options (still not the same as a person would do, but w/e).
you can practice punishing marth's attacks if you have issues with that by playing against a level 4-6 marth cpu and trying to pick the correct option OoS or from a dash dance before he's out of lag.
learn as many angles and from what distance you can recover with quick attack as possible. this isn't hard to do, just try to do whatever comes to your mind. see how far you can go off stage with aerials in ways that cover recovery options.
you can practice edge techs by setting a movement bomb thing on the edge and quick attacking up the wall of the stage.
also practice movement stuff with platforms. be sure to look up what shai drops are, they're awesome and not too well known from what i've seen. don't forget about edge cancels. get comfortable with various dash dance lengths, mixing them up, etc as well.
you can practice some combos in training mode if you want to, though the lack of c stick aerials is annoying there.