I bought base Grim Dawn and I cannot get the Warhammer 40k mod and the Better Levels mod to work. The game can see the mods are in my mod folder, and then they don’t work.
Then chances are good that you are extracting them incorrectly. And by incorrectly I mean that you are likely extracting them into their own folder. Don’t do that. Extract them directly into the mods folder, with no extra folders created.
Are you sure those mods don’t need the expansions?
Ah yes, that too - pretty much all mods require the expacs.