When I first took delivery, I thought I might be constantly shopping for accessories Thankfully, I found a few key upgrades and have been pretty happy with this (relatively) short list:
Screen protector (one that works with polarized sunglasses)
matte black console wrap
Tesla all-weather floor mats
Weathertech front and rear trunk liners (rear one absolutely necessary with that crazy rear window design flaw)
Replacement trunk and puddle LED lights (factory trunk lights are inadequate. Custom puddle lights are just cool)
USB hub to add ports for dash cam and a longer phone cable
Clear plastic ID badge holder for keycard when valet parking
roof sunscreen (makes a huge difference on the 100 degree days)
PPF wrap on front end to protect against rock chips
Spare tire/roadside emergency kit (great info on this forum on what to include, and what NOT)