Depends on weather, typically, when on the river, you must wear a CE approved helmet and buoyancy aid. A paddle is always useful, and of course a boat. Then of course a spray deck, or splash deck or, as I call it, a drip tray, that way it keeps out all the drips and keeps you nice and warm as well as prevents water coming into your boat. Thermal clothes can add warmth in winter and lots of warm dry clothes to wear between runs. Spare dry paddling kit can be an advantage to change into between practice runs and race runs.