I've been wasting pretty much all my time on this character for months now, here's what I usually practice:
)Handoffs, obviously. Practice getting 0-deaths on every relevant character
)Platform-to-platform shenanigans. learn what percents usually work with which characters (these are DI dependent but they're hype as ****)
)Shield drop neutral B in either direction, it pops you back onto the platform and shoots the ice block if done fast enough. Also practice shield drop aerials for learning l canceling and ****, but doing the neutral b's helps you be more precise
)autocanceled u-airs, best option in neutral 90% of the time.
)Sopo combos & tech chases, learning to react to either go for b-air regrab or u-smash after d-throw on floaties is helpful, and of course you have u-throw combos & tech chases on fast fallers. random DI bots are useful here. (pivot f-smash>nanapult is the easiest way to quickly get rid of nana, but if you're a real G you can dash dance blizzard at the edge and walk off to kill her. i end up SD'ing like a third of the time when I do this though so i stick with the pivot.)
)Actual combos. IC's can go crazy with the desyncs, you should be doing d-throw u-smash and d-throw n-air/u-air into **** at low-mid percents if they're good at mashing
)Wavelands and ledgedashes, plus ledge stalls.
Also, **** around with the timing for a little and you should be able to hit x or y on the frame of your dash dance to make nana jump alone. It's super fast and if they don't see it coming you can stuff approaches really well. This one is pretty hard to get consistently but it's just so nice
btw good **** for tearing up Montreal, you wobbled'em good