Just do stuff,
Reader level just goes up as you use site more.
Commenting is self explanatory as well.
Uploader level increases when people look at your uploads but decreases if your uploads get rejected for not following upload rules. It gives way too much points for the effort it takes though, a week of uploading will get you the same level as months of hard work on the other levels.
Editor level similarly goes up if you make good edits with tagging rules in mind and goes down when your edits are rejected. Currently edits barely do anything to your level though, so even just getting it above level 25 is very impressive
Tagging level is only awarded for making new tags, new content tags have to be discussed thoroughly with multiple moderators first (improvements channel on our discord is the easiest way to do this) because we need to be sure they fulfill a bunch of different requirements, people mostly increase it by uploading stuff from artists/circles, parodies/characters or scanlators that did not have their own tag yet.
Moderator level goes up if you agree with moderators on the pending section, upvoting edits that'll be approved and downvoting edits that'll be rejected; Its a pretty much useless one to track though, the idea is that if people that have proven to make reliable judgements pretty much every single time vote on pending stuff, moderators might not bother double checking an edit and just go along with the votes but we do this purely by remembering which people have shown to know their shit when it comes to tagging, not by looking at their levels.
Site level is just the total of these.
The Top contributor page shows the rankings for the highest levels on site but it has 2 bugs at the moment
-Tag creation level shown shows the reader levels a 2nd time instead
-The 6 seperate top 5s refuse to show anyone who isn't also in the global top 15, currently this discredits 2 editors, one of which should be at top on level 49 (will eventually get there myself but 41->42 already took me months, I'm honestly confused how he got that high without running out of stuff to fix) and probably about 80% of the people who should be in the top 5 commenters because those tend to be purely readers while uploading is essential to hitting that top 15.