Wrestling needs very little kit — but the one piece it does need, ear guards, is the one people regret skipping.
Head protection for sparring and competition.
Wrestling is equipment-light by design. Beyond something to train in, the only piece most wrestlers genuinely need is headgear — and specifically ear guards, which solve a problem no other sport has quite so reliably.
Cauliflower ear, properly auricular haematoma, comes from the friction and pressure of head contact against a mat or another body. Blood collects between the cartilage and its covering, and if it is not drained promptly it hardens into the permanent thickened shape that wrestlers and grapplers are known for. Ear guards prevent it. Nothing else does, and once an ear has set, no amount of subsequent protection reverses it.
That makes ear guards a decision to take early rather than later. If keeping the shape of your ears matters to you at all, wear them from your first months of training, consistently. If you have already started to develop swelling, get it drained by a medical professional promptly rather than leaving it — and then wear the guards.
Beyond that, wrestling kit overlaps heavily with grappling generally. A rash guard under a singlet reduces mat burn, knee pads are worth it once you are drilling shots on a hard surface, and anything you already own for BJJ or MMA will mostly carry over. Wrestling shoes are the exception, and worth having if you train on a wrestling mat regularly.