I am a fairly new detailer, So I will do my best to add to this topic. I used to buy cheap random orbital polishers until I burned up my 5th one, through frustration I decided to just throw money at the situation and purchase the most expensive random orbital that I could find. I ended up with the Cyclo dual head polisher and I love it but it can take a long time to do paint correction so I just purchased a Makita 7227 which I have'nt used yet. I would say it would in my opinion be most important to not mess around with trying to find an inexpensive polisher and just get the best right from the start. From what I see I would say either a flex or a cyclo for random orbital and either a Dewalt, Hitachi or Makita for a rotary. I could'nt do a good job without a good selection of brushes either. For brushes, I look at every brush everywhere I go whether it be the grocery store, dollar store, Auto parts store, flea markets or yard sales. They seem to turn up in the most unusual places. I got by in my first year on dollar store and walmart micro fibers and until I won a six pack of mega plush micro fiber towels from Poorboys, I never knew what a real micro fiber towel was so now I won't buy anything but. Pads for my polishers, I mostly use a light cutting, polishing and finnishing pads but the medium cutting and cutting pads are a must have for me as well although I don't use them as much. I use a one gallon pump up sprayer a lot for clay lube and apc and the like, I find it to be a big time saver. I would recommend various squirt bottles(not spray bottles) to dispense polishes with. Detailing apron to keep your belt buckle off of the paint is pretty important, I have over time collected many tools for scraping off door trim adhesine from missing bump guard on the edge of doors, These are things I just saw at various places and thought " Gee this would work good for" I always keep an open eye for something that might make the job easier. Be creative and I always think "will this scratch the car if I use it?" And if it will I usually don't pick it up. I can not have too many applicators either, All different kinds of applicators, Foam brushes make up brushes work good in a lot of places as well as acid brushes as they are a bit stiffer. A good strong wet/dry vac at least 5 horse power. A good power washer is something that is deffinately on my to purchase list. I know you are looking for the most important tools but every one of these tools that I have listed are all part of "my system of operation" and I would not be without any of them. I hope that this reply gives you some goog ideas, TD