What Sushi_ said is definitely important, but I'd also like to add that the game(s) you want to play and the resources your school has are going to make quite a difference. If the students are able to supply their own equipment (laptops, mice, etc.) then it's pretty easy, but if you need to borrow the school's equipment then games that require a lot of computers for a match (e.g., LoL, VALORANT, CS:GO) become complicated. Smash Bros is an easy and cheap option because all you need is one computer and a few controllers. Basically, just have a plan for what equipment and funding you need and how you expect to cover that cost (charging a club fee maybe).