Concrete is always good. Some put down a couple inches of pea gravel, but that is hard t walk on. Hard clay is used in old style shops. If you want something in sheet form, use sheets of cement board siding. It runs about $25 a sheet, which is about $0.75 a sq.ft.
You can just paint the existing floor with an epoxy or aliphatic porch/garage floor paint.
The best way to keep a new shop clean is to not let it get dirty. Sweep at the end of every day's work, and vacuum up where you can. Blow off the shelves regularly. Many of us delayed this process and now our shops are covered in dust and grinding debris.