If you get a cutting knife, you’ll also need a cutting mat to protect your table.
These are known as self healing mats - basically as you cut them, you don’t really destroy them. They just kind of ‘heal’ themselves. However, if you make lots of cuts on the same place then, of course, they’ll wear down faster.
These mats come in a variety of sizes and brands. I probably own at least one of every brand out there. Alvin and Artools are some of my preferred brands.
I don’t recommend anything smaller than 12”x9” and personally prefer the 12” x 18” size for everyday projects.
One last tip, do not leave these in any place hot, like your car trunk. They will warp! If it does warp, you’ll need to place it back into a hot space and lay heavy books on top to flatten it back out.