Utilize throws, shifty approaches and attacks, and the banana and peanut gun to get people into the air. That's your #1 priority: get the opponent in the sky so you can use those aerials. All of his aerials are buffed from Brawl and are very deadly, up/back/forward air are all high priority and give good knock back.
The bread and butter approach would be to just get the grab and do a down throw ---> up-air or back-air. It's a guaranteed combo and you can string a few b-airs at lower percents. Once you get your hits in try and keep up the damage in the air, and if they're catching on bait out moves in order to counter. Throw a banana up there to get some hitstun too.
We all know the banana has been nerfed to hell. Thing disappears after one hit and you can only have one on the field. But using the peanut gun and the banana together leads to good things happening. Use the peanut gun as the opponent approaches and either follow up with the banana if they get hit or throw it to the ground. I could go into specifics on this, but the jist of it is to make your attack shifty and unpredictable.
At any point you can throw out a side-b kick (press A or B during the jump), shoot a peanut, dash attack, short hop nair to pop them up, etc. Change it up a lot and see what works best. I personally love using nair to get them in the air to a few up-airs or back-airs.
That's usually what I try to do. If you want some good examples of high level play just watch Jtails on a tournament.
TL;DR: Your goal is to get the opponent in the air so you can use your buffed aerials.