I don't play this game, but as an GM/Admin for 3 different other games I can give you some factors.
Here are the main key factors for becoming a GM.
1. Professionalism
As a GM you will be part of the public face for the game server you are representing towards your community. In order to manage that in a long term environment you must have some kind of professionalism within you in order to engage within your community. Everything that you say matters between you, your staff, and your community. Always try to show respect and positive energy whenever possible and make sure that you know and understand your own community.
2. Skill Set
A GM usually has a special skill set that can be provided towards either the community or staff members. They can also be technical or personal. Technical can lie towards Database Operators, Coding Languages, Reverse Engineering or Building Scripts/Tools. Personal can lie toward Graphic Designs, Community Management/Moderation, Content Creation/Production, Support, or Testing new updates.
3. Contribution
Very important. GMs needs to contribute their works, effort, respect, and manners where ever if it's in a Private or Public environment (and must be able to differentiate between those two). This very much ties in between 1 and 2 in order to passively achieve 3.
4. Communication
This is the major key factor if you want to aim for a GM role after knowing the other 3. Communication skills are the most desirable when it comes to being a GM. Get to know how the staff, community, and servers operate within internal and external point of views and build up your relationship between all of those elements, and the only way to build them up is communication. If you know how to play your cards right, this is the fastest and effective way to becoming a GM.