Any tips on good places to grind fast. Tryna do something different this new playthrough.

Stack all Experience Boosts and Thunder Boosts you got, make sure Donald's Cure is turned off, acessories should be magic oriented (preferably Shadow Archives).
Start from the save point in TWTNW where you can face off Luxord and Saïx, go downstairs, take damage from the Assasins until you are at 50% HP or less.
From there Magnega and Thundaga will be your best friends to defeat all nobodies you face, personally I do this until I reach the first area of the castle, then make my way up. Special mention to Berserkers and Sorcerers, try to defeat the Berserkers asap, and Sorcerers are immune to Thundaga (but are still staggered by Magnega).
Ethers are optional, but you can use them to speed up the process if you find yourself constantly without MP while facing off annoying nobodies.
Should go without saying that Reflega can get you out of sticky situations, specifically with Snipers, Berserkers and Sorcerers.
Keep at it, and you should get fast level ups 🙂