well for starters maining is awesome, her abilities are outstanding over all
in order to main peach you will need to know three things, soon after that, apply other movements to her first actions.
Float Canceling; in order to float cancel you need to press on the jump and down on the joy stick while holing the jump. this can be used for out of the range forward smashes from the opponents so that you could Dair them from atop, and soon after you land you are able to attack.
Turnips; these are needed for range attacks, mostly useful against Marth and Ike cause of there swords, peach being a lite floater, she could easily be countered by them. Also good to annoy characters who cant spam and camp.
And of course her Down Smash; every one that know about peaches down smash hates her unless your the one that mainly doing it. Its not as strong as it was on melee but still does a good sum of damage while your opponent is holding down this works good on heavy characters.
Soon after you figuer these out, you’ll have a terrific peach.
If you have any moveset that you would like to discribe, please post here; as well as, tips and hints