Hey noob,

what exactly doesn't work?
It's up to you which server version you want to set up. Since you are posting in the et300 thread and I usually advise to use ET 3.00 - as it's the latest version - you could set up ET 3.00.

As to your question: 2.60b is fine.
Default the game runs on 2.60b protocol 84 while accepting also legacy 2.55 clients.
/JoNny