If the original Phantasy Star was released today, it would describe the following things as sidequests:
-Iala Cave/Iron Fang
-Drasgow/Sopia/Mirror Shield
-Any Laconian equipment as well as the Frade Mantle
You don't need any of it to finish the game. After getting the Luveno, all you actually need to do is get the Amber Eye, Hovercraft (or Land Rover), Ice Digger, trade Amber Eye for Eclipse Torch, Aeroprism, and Nut of Laerma. That's it!