I just started off on the market, earned 18k by buying and selling stuff alone. Not much, yeah, but I might as well explain how-
Did this by finding things being sold for much less than the original price so they would get bought. I also make sure it's a 'popular' item. So like, no ugly colours or items that nobody ever buys. I then buy the item and sell it again for a higher price. I always make sure there are no other duplicates of the same item being sold for a price too close to the cheapest one because then I can't raise the price much when re-selling it because people won't see it when they tick "Show only the cheapest offers"
At least that's how I get quick TC. I only get like 200 TC - 2k TC profit each time though.