The MFGG Wiki is always open for improvements, and since it's a wiki, anyone can make those improvements.
It is asked however that you don't take it upon yourself to sweep over massive changes to articles without consulting a Wiki Sysop first. You may wish to experiment in the Sandbox (or its talk page) before making a decision.
If you would like to help the Wiki team as a sysop or bureaucrat, feel free to give the Admins a call. However, the acceptance rate will be very low and will be judged on your past history at MFGG and activity on the Wiki. Don't count your chickens before they hatch, etc.
If you're looking for a way to help out, try looking for the list of linked pages without articles or articles needing expansion.