Exosuits
Exosuits are a little better off than their Starship and Multi-tool peers. For starters, they don’t have to get rid of anything in order to grow. You can hold onto all of your precious cargo and upgrades as long as you want. To obtain more inventory slots for these, you simply have to locate and buy them.
Scattered around No Man’s Sky’s planets are these large dropped pods. They’re hard to miss so just fly around until you see one. Inside is an upgrade for your Exosuit that adds one slot. The first one is free, but the price rises with each new discovery. You’ll definitely want every single one you can get, though. I found six on one planet once, and that’s not a bad deal.
Once you get an Atlaspass, you’ll also find upgrades in Space Stations. They’ll be in the previously locked areas, so don’t forget to look.