Finally got a work shop.

Nice. That's a decent size to be able to store all kinds of stuff, and work on anything short of the car itself. As others have said, I'd do flooring before doing anything else. Even rolled linoleum would work, and if I did that I'd let the edges come up to the top of the 2x4 base so anything spilled can't travel to the side and go down to the wood floor. That chipboard has no ability to hold up to extensive foot traffic or water.