Question

Which two commodities seem most important to the trans-Saharan trade

Answer 1

In Sub - Saharan trade, gold , salt and slaves were the most important commodities.
Gold came from Bambuk in the valley of the Senegal where there was a lot of alluvial gold. Rock salt came from areas in the Sahara which were once covered by inland seas. Its extraction, in large blocks under the blazing sun, was appalling work carried out by slaves.
Slaves mainly came from around the region of Lake Chad, where the Zaghawa tribes made a habit of raiding their neighbors and selling them to  Arab purchasers in the north.
Other important commodities were cola nuts, dates, copper and brass.

Answer 2

Basically gold, salt, and the slaves were the most important commodities.