I'm getting my first car Wednesday, and I'm needing a few parts to finish it out, but I'm not sure what to get! The car I'm getting is an associated b5m.

So far, this is what I will need.
Battery charger - venom pro 3 charger $79.99
Batteries - I'll need 1-2 (how long do they last nowdays?)
Motor/esc - hobbyrun xerun justock zero spec sensired brushless combo $94.99
Radio and receiver - getting a radio for sure with car, not certain about receiver
Servo - may need one, not sure what's good

Am I missing anything? And are the things I picked out decent choices? Thanks for the help!

Servo and battery life is going to depend on what car you're getting. Batteries for something like trans am can last 20+ minutes, similar with stock 2wd buggy but you'll notice some loss of punch after a while.

It's an associated b5m

I've got a savox 1258TG in my 2wd buggy and it's been great. Can't go wrong with the SMC shorty packs, they're cheap and pretty decent.

For the slightly less impressive BEC on the Hobbywing Justock ESC, I would actually suggest the low voltage Xpert 3000 or 4000 series servo. The Savox is a great servo but it can be hard on an internal BEC that is only rated for 6v like the Justock. Especially if it gets combined with Spektrum radio gear. With the xpert servos, they will run great even down to 4.8v and will have plenty of torque for 2wd buggy