Note that prices for the bases'/planets' top exports/imports will change wildly for each new game. Ascii Sector generates a new random price landscape at the start: "Preparing commodity market...". So e.g. transporting 1x gems from Andingmen to New Beijing can make 220 credits in one game but 40 in the next. Therefore understand that the following are only suggestions worth trying, they always do generate profit, but your milage may vary:

  1. A fast guide is, Buy grain at Basin; Transport that to Slavneft, and buy advanced fuels. Transport the fuel to Hooper's Hope, and buy gems. Transport the gems to Pyrdion, buy nothing; then, fly to Basin, and start the whole thing over again. (Quoted by: Lexus | Originally written by: VincentFirePony)
  2. Buy wood at Basin, take that to Hooper's Hope, where you sell the wood and buy as many gems as possible, followed by as much iron as possible.. Take the gems and iron to Basin, where you buy luxury food and sell the iron. Continue to Pyrdion, where you sell both the gems and the luxury foods and return to Basin. (Quoted and originally written by JMaxchill)
  3. Buy iron and gems, with gems being the priority, at Novy Norilisk (Mendeleev sector), then go to Ragozin (also in Mendeleev) and sell the gems and iron. Buy as much mining equipment as possible, then plastics, and fly back to Novy. Repeat. (The advantage for this trade route is not that its profitable, but very fast, thanks to the fact that its all in one sector)
  4. (enter your own favorite trade route here)