The difficulty of the river you'll be floating and your aggressiveness will determine what type of tube is best to use.
A standard tractor-trailer tire inner-tube is all you really need to stay buoyant.
Plastic Inflatables can be very comfortable with features like cup holders and storage containers. Those inflatables with backrests may restrict movement while paddling and maneuvering.
If agility and durability are the two biggest concerns for your adventures then 600+ denier polyester (canvas) covered river inner-tubes with handles will give you the most control and protection.
Tubes made for towing may be too large to allow solid paddling, or be awkwardly shaped, but hey, giving up a little control and being at the mercy of the river is a big part of why we choose the tube over other watercraft.
Some of these tubes have numerous patches and other custom features.
Beer/Drink Holders built for class III rapids.
Extra clips for attaching dry bag / container and butt pad.
SAFETY NOTE: Anything tied to you or your tube may get snagged and hold you under the water, possibly resulting in drowning. It is important to tightly attach anything that cannot be free floating. Mesh bags for clean up should be too small to wrap around your arms or legs.
Life Vests should be worn at all times when the water is even just choppy. On still water the life vest usually becomes a back rest. There are many types of life vests, and again, the difficulty of your float down the river will guide you to the right one. We have found mesh-back or backless life vests to be the most comfortable when sitting in the tube. The tube will push up on any low-back life vest as gravity pulls you into the tube. Here is one example.
Webbed Gloves are a big help. Whether paddling hard to hit a rapid, positioning for a rock stall, grabbing the current to avoid eddies, the added surface area the webbed gloves provide gives a solid boost in mobility. Also, the gloves allow you to use your hands as rudders in turbulent water, and to "push off" and "hold on" to the water for better balance.
Shoes that will protect your feet are important. Flip flops won't cut it if you end up in the river. Waterproof hiking shoes are good. Keen makes great tubing shoes because of the toe & sole protection, breatheability, and siping. Most old skate or tennis shoes will work as long as they stay on.