yeah you really need to make a plan for the car, a budget overall then split the budget into areas say engine, trans, diff, spring/shocks, wheel and tyre, brakes, sway bars and chassis bracing, bushes and rubbers, and one for random other expenses
have an idea of what you realisticly want from the car, why you want it then look for products to fill the wants. just build it up over time with good quality stuff, rather than buying it all now and having lower quality gear. really depends in what you want with the car and how long you will hang onto it.
brakes is fairly easy, start with a fluid change and change the pads to something like the A1RM from GSL Rallysport (site sponsor). if you wanted to spend more you could go a ve upgrade which will need complementry upgrades like wheels if you dont have a minimum of 17 inchers. or even a set of 2nd hand hsv brakes maybe.
suspension could start with just a basic fe2 or kings lows and some monroe gt sport (i think) shocks but you could go some more expensive springs and adjustable shocks all the way to a coil-overs.
then stuff like bigger swaybars (dependant on the spring/shock rates, so do this after) or adjustable sway bars to fine tune the car.
then you'll probably change out some of the holden rubber bushes with some nolathane or similar while you're doing all this so add this into your budget.
but it all comes down to having a good plan/budget, and getting your hands dirty. nothing feels better than looking at your car at the start and the finished product and feeling, yeah i did that.