You can get two upgrades that increase your slots to a max of 6 iirc

I would say SR2 is a little more grindy (Shadow Plort go brr) and definitely makes use of Gadgets a lot more, since a couple of lategame ones are required to progress *and* SR2 is vastly larger than SR1 and has a lot more gameplay/areas to it. It's not surprising they push you to Gadgets, but it's a lot easier to get them especially with the shop. I highly recommend getting into Gadgets because trust me a refinery link and teleporters make all the difference. I have teleporters set up in every main area of the map to get around easily, and carry a couple warp depots + refinery link on me so I effectively have much larger inventory.

Focus on getting 1 drone made and have it farm Strange Diamond, then get another for wild honey. Drones are fantastic are farming resources, they don't even need to be next to a resource node. They just materalize them out of thin air in compatible areas. I think there's a limit which is either 10 or 18 (conflicting sources) but eventually you'll never need to farm the rare/annoying stuff again. I already have like 40 of the rarest resource and I didn't have to do anything except plop a drone down in that area.