Hello. Of course, if you are under 13 (16 in some countries), then the use of FANDOM is prohibited. VSTF are chosen by staff. You can look here if you want to join as a team to become a VSTF. VSTF are chosen by FANDOM Staff.
Yes, the more you report any spam or vandalism in the VSTF Wiki, the more likely you are going to be chosen by staff. But that's not really the case. Your reports needs to be relevance.
Here are suggestions to get started:
Revert any spam or vandalism you saw in any wiki. It can be Community Central, your favorite wiki, etc.
Report any spam or vandalism that needs to be handled by VSTF.
Don't start doing something that might ended you get blocked. In another words, don't get blocked from any wikis just because you were doing unnecessary.
So, I was looking at some of the VSTF members who haven't been super long time editors and it looks like if you have under-represented language skills, you can shorten the process. However, for regular English language VSTF members, you'd probably have to be exceptional.