I looked into 500ish + Deane. Money pit unless you have super skills as a mechanic to do it all yourself + parts cost quadrupled my new goal of around 400 give or take.
As said, usable power and balance is best. I agree 100% + you'll have more fun not worrying about slight noises.
Best thing to do is lighten the front end, remove stuff that is not needed and lighten things that can't be removed such as air filters(some cheap ones weigh double a decent one), air con (remove), fmic (cheap are heavy), cast metalwork (replace with custom parts), battery (boot), get a fast road/racing flywheel(revs much quicker due to less weight but also decreases engine braking), suspension (lighten), wheels(lighten), seats, trim etc... and so on most of these are cheap and easy to do yourself which I've done or am doing.
As for polybush, I'm doing the whole car.
1, it stiffens everything up
2, longer wear time as opposed to stock
Be prepared for a shock on the price front if you do it all and expect a large chunk of your wages to disappear.
You could get away with doing the obvious though round the hubs and arb's - Cheap enough
You can also do cool mods like an IC spray, for trick results use a temp sensor on the switch
costs peanuts to DIY.
Anyone who's had a very fast car will tell you, fun but you've always got that feeling of uh-ohh
My first fast car cost around £22,000 from buying the car for 4500 to adding bits, mapping etc... on hindsight I went too extreme and it cost a fortune to run, barely did 100 miles to a tank if driven fast, brakes squeeked if not used for a day, drove like shit at low speeds in stop go traffic, needed oil changes, additives, new brakes all the freakin time and my left leg was like a hulk leg when I sold it due to heavy clutch + I barely had any money to have a nice life. I was eating pasta and tuna for dinner and tea, eating at friends houses etc... as I spent all my money on running the car. Sold it for half what I paid >.<
Wish I'd just stuck with 350-400 ish and focused on stripping it, chucking a nice bose system and handling - would likely still have it now.