River surfing can be tough to learn for beginners, and it can be dangerous without the right gear. Here is what you need to get started.
No single board works well for all conditions. Instead, most surfers will develop a set of boards that work well in their area. Some start with traditional ocean boards, but it's not an easy way to start. It'll be easier to learn if you start with something with more volume and a larger planning area than most ocean shortboards, and less length than the long soft top boards that most ocean surfers start out on so you can fit onto the wave. Look for soft top boards with significant rocker.
Save fiberglass boards for when you have your feet under you a little better, and do not drive your board into the rocks quite so often.
Helmets are almost mandatory at just about every river wave. Look for something whitewater specific rather than a bike or climbing helmet.
Wearing a leash is the eeasiest way to get killed river surfing. If you feel like you need a leash, get something as a quick release around your waist.
A PFD is a good idea in high-volume rivers, particularly if you're in a situation where you may be held down for a while.
Some foot protection is going to be important; most rivers are shallow and many urban corridors will have glass and other trash in the rivers that will cut up your feet if you're not careful. You need to look for a trade-off between protection and feel for the board; generally you can get away with something thinner than most people kayak with, but test things out for yourself to see how much thickness you want.
Unless you're only surfing in the heart of summer, you're always going to need something more than swim trunks to keep you warm. Wetsuits are the way to go here; a 2: 3 wetsuit (2mm on the arms and 3 mm on the chest) can keep you warm enough for many conditions, though a 3: 4 wetsuit is not a bad idea if you're surfing in a colder climate. If you want to do things the hardcore route and surf through the winter, you may be in the market for a drysuit. They're pricy, but they're worth it if you're building up ice on the banks or on yourself.