You don’t NEED any equipment to compete especially as a novice, but it does help. As you advance, there is certain equipment that is worth investing in to keep you safe, injury-free, and give you an advantage during competition.
Hard Belt: This is one of the first pieces of gear you should purchase. The bulk of your training should be belt-less (unless injured) to help build up your core. However, when lifting heavy or competing, the belt helps significantly. Make sure you know how to properly use one and brace your core.
Knee Sleeves: As you squat more/multiple times a week, these help with joint support, minimize the risk of injury, and aid in performance. I also wear knee sleeves for most moving events in strongman.
Elbow Sleeves: Like knee sleeves, elbow sleeves help with overhead movements, and moving events.