Reddit reviews Oxbow Animal Health Chinchilla Deluxe Fortified Small Animal Feeds, 5-Pound

Don't forget timothy hay!

As far as food, make sure to get a type without a lot of "junk" in it-- just plain pellets. I use Oxbow Chinchilla Deluxe
and make sure you get some of their old food so you can make the switch gradually if you need to switch from what they are currently eating.

Start calling around to find an exotics vet who has experience with chinchillas. Chins don't need to visit the vet regularly but you need to know who to have on speed dial in case of an emergency.

I highly recommend investing in the Ferret Nation Cage (if you buy one used, avoid one that's been used by a ferret though-- yuck. Speaking from first hand experience) and using fleece liners. My chins love their large metal flying saucers. As a rule, chinchillas shouldn't have any plastic in their cage--- some chinchillas are more voracious chewers than others, but you should be aware that some chinchillas have died from digestive issues caused by ingesting plastic.

They will also need a hidey house-- Most pet stores don't sell any good ones, so if you can, it's best to build your own from kiln dried pine, or there are some online sellers who build them especially for chins.