A book on brewing potions, a large amount of supplies and a cauldron.

The invisibility coat

A vial of felix felics

I think a Lunascope would be a neat thing to have

Hermiones purse. Imagine it, you could live in that thing. Tidying your place wouldn't be a problem. Have some very private possetions that you don't want visitors to see? Put em in there. It is so useful. Other than that, maybe a few self cleaning kitchen items would be nice

Harry’s invisibility cloak would be cool

A time Turner or an invisibility cloak