The foil itself is the key item, they come in a variety of sizes but the most important thing is that it matches your board.
Most foils fit boards through a specific type of fin box; a deep tuttle box. The tuttle box is commonly found on larger slalom, freeride and formula boards. They are usually pretty good for foiling as increased width of a board gives you more control and higher volumes mean you can get out in the lightest winds.
You can get foil specific boards and foil ready boards. Here the fin boxes have been further re-enforced and have a large array of footstrap positions giving you multiple tuning options. You can even get foil only boards, which see super sharp rails and very flat decks designed around the idea you’ll spend all your time above the water.
Any sail will do, although a few tuning tweaks may well need to be made especially when it comes to harness lines, which you tend to use on a much shorter setting when foiling.