What has been done to the car?

Open Cone/conical Air filter(any good K&N type will do) Spectre filters are good at a good price.I would lean you towards AEM dryflow, I had most others but staying with AEM from now on.

Make your wastegate adjustable if not already.

Tune up....Plugs and wires atleast. NGK V power plugs or good Delco set, I use NGKs. Wires, autozone duralast brand works just fine, same as my taylors or order some taylors from summit.

If you got a good exhaust system (no rust/rot pipes) a set of Turbo mufflers would be great. summit, dynomax, even cheap autostore brand would be ok. (turbo mufflers,no flowmasters)

A universal hi flow cat would help also. Depending if you got alot of miles on your stock one. Most hollow them out but, three factors I don't like about that. 1. it affects flow/sound of exhaust, 2. bad for earth. 3 hp gain isn't that much more then Hi flow unit of today's tech.

Electric fan Convert, Ford 17'' Taurus fan or Lincoln/Mercury 18'' Fan would be great,cools even Big Blocks with ease. or atleast Flex Fan with spacer.

That's as cheap as it's gonna get,or that I can think of..... then addiction sets in.
Everything listed by RegalTType85 plus capping throttle body coolant lines and installing 160 stat. Thats bout it for cheap mods, but even after that it wont be enough you'll keep wanting more and more!! Welcome to the addiction!
and any suggestions on what wastegate i should get?

Your factory unit should be fine. (if it's in good working order) If it is not adjustable, you could make it with some simple hardware parts N tools. Someone might have a link to a DIY page.

What shift kit, fuel pump & regulator do you have ?

Do you have a G80 code underside of your truck hood? If so you got a posi, which is good to have.
im not sure what pump or reg. my dad is having the guy do it. i have not talked to him. shift kit either. i just bought the car. and do you have a link because i want to make it adjustable. and where is that code?
The code is located under your truck deck/lid. There should be a sticker on there with all the codes your car came with(power windows,bucket seats etc)

If not then just do a burn out and see what's the aftermath. one tire mark or two. As for pump and regulator, I would hope he knows to get a 255plh pump with hotwire. Many turbo buick vendors sell them, Turbotweak,racetronix, kirbans, full throttle speed etc.

For the wastegate, let me see if i can find you a link.