I think there are two main uses for cock rings; to be tight on your cock to restrict bloodflow and make you harder, and as a penis-mounted vibrator. Some toys will be able to do both.
There are plenty of low-cost, no-tech options for the first. Most of them are stretchy rings, but you can also get metal ones (heavier, colder, no stretch). You should be able to pick some of the stretchy ones up for pocket change, so if you try them and don't like them it won't feel too disappointing.
Measuring yourself is useful too as they do come in a variety of sizes and, as you can imagine, fit is important.
There are guides on the internet (like this
Lovehoney one), but you basically use a measuring tape to get your circumference, and then divide that by 3 to get the diameter (3.14 if you want to be more specific
). You want a ring with an internal diameter a little smaller than that as you want the constriction, but not overly small as you don't want to throttle him.
The metal ones are perhaps best saved for the more experienced user, as they have no wiggle-room, and can't be cut off without power tools.
And then there are the ones with a vibrator attached, and these can be good for some hands-free clitoral stimulation.
They start out super cheap, with little LR44 battery powered vibes, but you can also get more expensive ones with rechargeable batteries, remotes, and even app controlled options. They also come in lots of different shapes too.
Personally we prefer the broader surface area models as the rabbit ear ones (etc) can get a bit pokey-jabby, and the clit contact can be hit and miss. Likewise, we prefer to use them in more 'grinding' positions to maximise the time it's actually useful.
These don't tend to come in different size options for each model though, so you may find one that's the perfect vibrator, but the cock ring itself is a poor fit. If it's too loose you can use a simple stretchy cock ring to pad it out, but be careful you don't overload yourself. You can also turn them upside down for positions from behind, and this can help them stay in place if they're loose and a bit top heavy (you get a little gravity-assist
).
We actually don't tend to use them a great deal any more, but our favourite one is this
Mantric one.
Hope this is useful.