Chainmail is nice to make. You need some pliers, some rings, and some knowledge to make it
You can use any pliers
To start off, I'll walk you through how to make European 4-in-one, one of the easiest weaves (ways that rings are combined). My belt is made solely out of European 6-in-1, an extremely similar weave.
For rings, you can find them in various places such as here.
The aspect ratio (the ratio between the diameter and the thickness of the ring) is useful to know, and determines what weaves u can make
Now we need to figure out how to chain rings together. You do this by opening and closing rings
To open a ring:
To close a ring
Now you are able to put rings together, now we just need to figure out what rings to put together
This site here gives a guide of how to combine the rings for European 4-in-1.
Good luck.
There are a lot of other weaves. In particular, I recommend going for the Persian 6-in-1 or Byzantine. They're good weaves for bracelets or necklaces.