Mentally, have an ever-adapting and curious mind about what your rabbit reveals he/she needs (Maybe he/she is a particularly “bad” digger and you’ll need to get some tiles to lay down. Maybe there are a couple corners he/she likes in the pen to do business, so you’ll need another litter box, etc.). Also, keep in mind your rabbit will be ever growing for the next year plus, so if you have a smaller box/pen, you will need to upgrade as time goes on!
Grooming tools would be helpful. You don’t need to start nail clipping and brushing right away necessarily, but having them and maybe just getting your rabbit used to the tools and their sounds/sensations may be good. This includes nail clippers (usually the small cat ones) and a brush/comb (keeping in mind you want one that will be effective, but not harm the rabbit’s skin).
I am bias towards reducing pet-related waste, so I recommend thinking about buying some rabbit-task-specific towels (I use small, kitchen square ones) and a laundry bag to store dirty ones (I use a cloth-diaper bag; meant for cloth baby diapers, so very odor-blocking and antibacterial), so you’re not constantly going through paper towels. It’s also helpful at first, when your rabbit is growing up and may feel that urge to mark…everywhere due to emerging hormones and being in a new environment! Also, depending on your living situation/preferences, perhaps a designated trashcan specifically for rabbit hay/litter/poop/pee items, so it’s consolidated in one spot. Some people don’t care though. I also recommend baby diaper pads (washable), which I use in lieu of the disposable puppy pee pads – they are helpful for lining your carrier (also need to get this!) for trips or places accidents may happen frequently. I put one in front of Wick’s litter boxes, in the case that he pees over the box while in it or he gets lazy and just pees near the box, rather than in it!
A small dust pan/brush, or a large one would be good for sweeping, as hay and litter (if you do not have a litter screen) will get everywhere as a general reality of life! It can be loud and unruly to get a vacuum out every time, so a quick dust pan works.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.