If the normal 70 item inventory seems too small, you can buy backpacks to raise your limit. You can buy a backpack at each of the following locations, and increase your limit by 10 with each backpack.

Gorhart: The Corner Shop
Ysa: Asker's Alley
Adessa: Domus Politica
Rathir: The main Scholia Arcana building
Mel Senshir: The central courtyard area

Good Luck