I said nothing about buying anything.
Finding out what you want is as straightforward as reading up on what certain parts do, how effective they are, and comparing that data to what you think is missing on your car. I bought my first MR02 with only four additional items: bearings, drift tires, a 94MM motor mount, and an NSX body. I read everything there was to read on the MR02 at the time, and decided that I only needed those four things to get started doing what I planned to do -- drift an MR02. Only later on did I find out that I needed damping (symptoms: poor on-throttle drifting) and thus ordered one of those. As long as you have knowledge, even book knowledge, you can apply it and save yourself money.
Especially comparison tests, if you don't want to buy things to compare yourself, find someone else locally or online who has, and find out what they have to say about it. Thanks to people like yasuji we know that that the latest PN mounts (LCG 94 and LCG 98 V4) are the absolute best that have come out so far; no need to go out and buy the other ones we now know are inferior.
This is why it's important to ask local racers for what one needs, because every track is different and like you said, playing around with setups is expensive. There's so much data out there for standard Mini-Z's it's ridiculous, all you have to do is look in the right place and you will get more than enough information.
For example, if you raced at ILR or Kenon, I could be the guy to point out exactly what your MR01 needs: tires, top shock w/ grease, hard front springs, hard t-plate, and bearings. That will get your setup to 90% of what's ideal... no, not perfect, and your car may not be the fastest thing out there, but it's enough to be able to enjoy your car on the track and run well in the Sportsman racing class.
2jack - Motor mounts are unnecessary until you need to run a 10t pinion, and even then you can mod the stock MR01 pod to do so. Absolutely pointless to buy a new rear pod before you even know what the benefit of an alloy one feels like.
Again, I stress the point that you can find out what you need simply by asking the right people, and not us, because I have no bloody idea what your track looks like or drives like!