Step 1: make it pass tech: Cage, Seat, Kill Switch
Step 2: Maintenance items
Step 3: "Racecar" stuff. This will likely be after your first event. This includes changing suspension geometry, upgrading marginal parts with performance-ish parts, lightening, etc. Everyone WANTS to start with this. But this is probably the #1 mistake newbies make. If this is all what you want to do, buy someone's hand-me-down and improve on their car that's already passed tech once before.
Experience shows that you will run out of time as the race gets closer. If/When this happens, you can (and SHOULD) show up anyway to the track with all of your parts in tow that you "just didn't get to yet."
There will be 50 people at the track who can put brake pads on your hooptie, 60 who can put in a new thermostat, radiator and hoses, and 100 who can paint numbers on your doors for you (ok, maybe only about 3 of those). Even 15-20 who can help you put in a new engine or transmission. But there will only be MAYBE 3-4 people there who can weld up a cage AND maybe only 1 or 2 who have a welder AND who aren't already committed to some other cause.
Cage takes dozens of hours. Mounting a race seat takes a good day. Installing a kill switch takes about half a day. All of those are considered "Fabrication", more or less. You want to avoid doing Fab Work at the track.
Welcome-- we ALL want to see you out there.