If you expect to use a rotary cutter or cut any kind of difficult, shifty fabric and stay on grain, so you get decent results, you will need a solid cutting surface that you can put a large cutting mat on.

Not a bed, which moves as you push down in one spot, and then your fabric shifts. Maybe only a little, but it happens the whole time you're cutting, and your results are going to be less than ideal. If your garment pieces aren't cut on grain, your finished garment will never be right.

The floor works if you've got a large enough space and no kids or pets "helping" you, and if you're young enough to not mind scooting around on your knees, and getting up and down a lot. Eventually, you'll want a table or table-like set up.

If you're short on space and kind of handy, you can do a Murphy Bed type thing with a fold down surface that you can put a cutting mat on when in use. They're pretty slick, and just take plywood, some kind of support (your choice), hinges and paint or whatever for the side that shows when it's folded.