This is the toughest way to do it, so you have to make sure you have the plan for the final results all figured out and then you can work towards it. Change anything along the way and you can potentially undo what you've already worked towards.
If you just need to get it on the road and have the original suspension, the I'll stick with Monroe Gas Matics as the low cost suggestion to get you rolling with something that is miles ahead of the orginal oil shock package.
If you are looking for longer term package approach, perhaps utilizing the Hotchkis components would make the most sense. As time allows you can spend a few hundred bucks on each component until completed. Start with a pair of front Bilsteins. Then rear Bilsteins. Then a front sway bar. Next, rear sway bar. After that, torsion bars. Next would be leaf springs. If you are still wanting more, then maybe the upper control arms, and finally the bump steer correction tie rods.
The drawback to this approach is that while shocks and sway bars are bolt on deals, once you start swapping t-bars, control arms and tie rods, you will need to get an alignmnet after every change. This will inflate the budget compared to putting those items on as a package.
Speaking of alignment, getting an alignment that is more radial tire friendly, assuming your using radials, is also a key part of this. Radials tolerate a wider range of adjustment than the original bias plys, so if you put the original alignment specs on the car, you are giving up potential performance. If you haven't done so already, I'd suggest as much positive caster as possible, up to 4-5 degrees. Add negative camber of .5 degrees. Total toe in should be 1/16 of an inch of the equivilent amount in degrees.
