Completely pointless buying one that is ‘ok’
No, it’s not. Even the cheapest one will be steadier than hand held and will support the camera without you holding it. So not pointless at all. You can use the self timer as above and if you have it, the mirror delay function that flips the mirror 2 seconds before the shutter goes. Obviously not ideal but still better than nothing.
Yes nicer ones are more durable, and will reduce camera vibrations, but it’ll still be steadier than hand held. Only worry with cheap crap is that it might not support the weight of your cam so the lens might droop.
Monopods are a funny old thing. You need to know how to use them properly otherwise they don’t do much, but with a bit of creativity you can do an awful lot. I had one before I had a tripod, so I’d do things like strap it to a railing or wedge it against a tree with my body for a solid tripod like support. It’s surprising how much you can do with just one leg. Depending on snow, if you are boarding you could stick it in the ground for self support 🙂 They are also quicker to get out and set up than a tripod.