AT, HTS, Services. As the central 3. electric components, electronic components, industrial eq, machine parts. as the secondary level. but thats kinda the skeleton of my ASQ
additionally, other corps that really crank out a profit, if you set them up right. home eq, clothes, HP, med eq, med mat, pharm, plus many others.
when it comes to selecting corps. of course we all look at whether the product is in the red, and what kind of education level you'll need to maintain... further thoughts... look at the supplies, if it uses allot of the consistently red supplies, then its supplies itself will contribute more to other peoples profits than your own. Books and Newspaper are an example. And opposite example, look at Cars on FB, one of the key supplies, car engines, are a third the cost, compared to other planets. meaning cars have a greater profit potential on FB than WG.
even more consideration. their are allot of corps that require a mid-range, or low amount of techies. by running high sals, you jack up salaries of high payed professions (like High tech Seniors,) lowering "profit," but you get it back via income tax, and probably "country resources used," by going with lower tech corps, you can save on education. and then buy lowering salaries, you compensate, by having your corps making higher profits, and corp tax/payouts. this secondary method, also has the effect of lowering your gov and military costs...
i guess to sum up about corps, nearly anything can work, really well, its all in how you set up your country.
as far as buying/selling from the open market. i'm being pretty successful with aluminum, copper, iron, machine parts, solid missile fuel, weapons parts, wood, cattle, gold, and silver. But i'm doing my thing via space trade.
the way i've got my space trade thing down, i make between 10-15GC per shuttle. If i build them myself, they cost me between 4-6 GC... and you can take a look at the prices from direct trading.