Easiest way to get your car ready, is to inflate the tires to max and enter an event! One thing I learned through the years is the driver is the biggest component, and a novice constantly changing his/her car can impeed learning.
But in changing a stock car to getting it ready to autocross this is the order I would go in:
1) alignment: get some positive caster, negative camber, and a skosh of toe in. Use the Moog bushings and it will be much easier to get that. If not, you may need UCAs, but this is where it all starts.
2) 200 treadwear tires as wide as possible. Tires make the most difference when transforming a car. However, the difference is two fold. While a sticky tire is faster, it forgives many mistakes. That can slow down learing the fast way around a course. Locally I chase down cars on 50tw tires on my 200tw tires. I'm not the best driver but last time out I wasn't last in my class, either.
3) Frame connectors. If not done already, they can be done as cheaply or as expensive as you want. Go to a steel supplier and fab your own or buy the latest and greatest contour fit. Something is better than nothing. Get a bolt in set and bolt them in, take them to an exhaust shop and get them welded in.
4) sway bars. Go big in front, like 1 1/4. For the rear, start small. If the car still wants to push and not rotate, go bigger. Repeat until the car just wants to kick out to your driving style.
5) shocks. Get good single adjustables to start. You can stiffen them up for racing and then soften them for the drive home. If you go big torsion bars and keep cheap-ish shocks, you may hate the ride on the car over roads. That's why I say shocks first.

That's where I'd start. Don't worry about oil mods at first unless you're triggering the oil light. a good oil pan isn't cheap, and changing one while the engine is in the car isn't always easy. Changing spring rates is also easy, but it gets more expensive, and again, a lot is driver preference. There are some of us that like the large 1.18, 1.22 and 1.24 bars. Hotchkis, among others, recommends a smaller bar. It all depends how hard core you go, really. There's a lot more to go, as with any motorsport. How fast do you wanna go? $$$$$