Well, ofcourse RE is important but you also need to be somewhat familiar with network programming(stability & all).
As a first step i would try to get used with the game itself, you need to know your game

Then start with the basic things:
How does the client communicate with the server?
How does it process the packets?
Encryption?
Get familiar with the way the client handles the packets so you can start sniffing and reversing the protocol.