MS Paint is commonly used and you do not need a tablet. With enough time, anyone can make sprites. In-Battle Sprite Guidelines Getting Started If you want to see what has been done, or want to contribute, check out one of these pages.
Gen /vp/ is attempting to use as much original material as possible. The quality of spriting, both in-battle Pokémon sprites as well as overworlds and map tiles, can make or break a game. Sprites, after Pokémon designs, are the backbone of a good Pokémon game.