can u get a rare circlet with 0 sox to get 2 soxs?

No. It must spawn with 2 sockets.
Larzuk will only give it 1 socket.

Not possible sadly.
Lazurk can only give it a Max of 1 socket.
On magic items, you can get 1 or 2 sockets.

In order for a rare item to have more than one socket, it will have to spawn that way.