What kind of changes are you proposing? Are they large changes that would need to be discussed? If not, then you can probably just go ahead and make the changes; the wiki is very informal.
If the changes are big or controversial and need discussion, then the chat channels at https://chat.gnome.org might be a good place to discuss it, or find out from there where would be the best place to discuss it, depending on what the change is.
You do need to be verified to edit the wiki, though. I believe there are instructions on how to get added to the verified users group on the wiki, but if not, just ask in the chat.
Or on Gimpnet (for IRC) or on the Matrix side of the bridge at e.g. #newcomers:gnome.org, where most contributors are (since in practice there isn’t much chat happening on the Rocket chat).