Can I assume OP already has bolt ons and a tune?
If I had a stock car and purely wanted to race it at the track and only had $2000 to spend then that money will be spent thusly:
4 Yokohama AD08's - $1100
Rear Swaybar - $250
DBA4000 Slotted Front Rotors - $400
QFM A1RM Brake Pads and some racing brake fluid - ~$200
Those mods meet your budget and will give you the biggest gains per dollar spent at the track. Notice how the biggest gains are all in the consumables?
The main issue here is, we don't have pure race cars. We drive them on the street, so for that reason I would want to at a MINIMUM get a stage 1 AP map because that makes it so much more fun to drive. In that case the tyres and brakes can wait until they need to be replaced and we can spend some money on power mods in the meantine
Suspension - I spent BIG on my suspension setup and to be honest, the gains were fairly minimal in terms of raw time. My PB really didnt change much when I put the coilovers in, what improved was my lap times consistency.
Outright power mods depend a lot on the track you're racing at. Power matters at Eastern Creek, but at Wakefield Park it doesn't mean much at all.