As I've posted in other threads, I have the protectmytesla.com carbon fiber mudguards and they're fine. Cost a little more now than when I bought them. They protect against alot of road debris, but not all. They're equivalent in size and shape to the California model mudguards by antirouille Bolduc. He has three versions and the California is the smallest. The other two are for more severe conditions like you might face in Quebec or Finland, etc. Boutique - Antirouille Bolduc Of course, Bolduc's mudguards are rubber, I believe. Also, if you have AWD, you're going to get more debris thrown up by the front wheels, than if you just have RWD.
If you want to go the PPF route, you can DIY the rockers, and the lower part of the doors. Also the area behind the rear wheels. That can cost $200+ at 2018-2019 Tesla Model 3 3M Pro Series Clear Bra Rocker Panels Paint Protection Kit
I've done the hood, fenders, rockers, doors, mirrors from pre-cut PPF kits at InvisibleMask - Paint Protection For Your Car
If you want to go the PPF route, you can DIY the rockers, and the lower part of the doors. Also the area behind the rear wheels. That can cost $200+ at 2018-2019 Tesla Model 3 3M Pro Series Clear Bra Rocker Panels Paint Protection Kit
I've done the hood, fenders, rockers, doors, mirrors from pre-cut PPF kits at InvisibleMask - Paint Protection For Your Car