There are five main ones.
Extraction
Exports - Minerals group, some Metals group, hydrogen fuels (chemical group)
Imports - Consumer Items, Food, explosives (chemicals), mineral extractors (machinery), H.E. Suits (technology), basic medicines (medicines)
Refinery
Exports - Metals, Industrial Materials, hydrogen fuels (chemical)
Imports - Consumer Items, Food, Minerals, hel-static furnances (machinery), H.E. Suits (technology), scrap (waste)
Industrial
Exports - Machinery, Consumer Items, food cartridges (food), computer components (technology), scrap (waste)
Imports - Food, Metals, auto fabricators & robotics (technology)
High Tech
Exports - Technology, consumer tech (consumer items)
Imports - Food, Machinery, Metals, superconductors (industrial materials)
Agriculture
Exports - Food, Textiles
Imports - Consumer Items, crop harvesters (machinery), agri medicines (medicines), pesticides (chemicals), biowaste (waste) [most other systems export this - cheap & plentiful!!]
Take a minerals group from Extraction to Refinery
Take a metals group from Refinery to Industrial or to High Tech
Take a machinery group from Industrial to High Tech or Agriculture
Take a technology or consumer items group from High Tech to Agriculture
Take a food group from Agriculture to any other system type
Generally, take biowaste to Agriculture systems, and take scrap to Refinery systems. These are widely available, and cheap, but won't deliver much profit in absolute terms.
And keep notes. At your first system see what's in high demand to be SOLD into the system, then travel off, and use those notes to decide what to BUY and bring back.
Ignore what the bulletin board missions tell you is 'hot' right now. That doesn't bear much relationship to the system's economy type, and covers commodities not yet available (e.g. I've seen 'wood' requested - not available to buy/trade, AFAIK).