Why is there no reputation tag?
I tried to
enter a new tag, but only users with a high reputation as 300 are able to generate a new one.
In essence, you receive reputation by contributing to the main site. This is achieved by any one of the following:
Ask a question that shows you've done some research, but still need help solving. This should include a minimal working example highlighting the main problem and be isolated to that problem only. Upvotes on questions earn you +5 in reputation.
Write up a good answer to a question. Upvotes on answers earn you +10 in reputation.
Write up a great answer and have it accepted by the questioner. Accepted answers receive +15 reputation.
Write up an awesome answer and be awarded a bounty by some donor (questioner or otherwise). Bounties can earn you anywhere from 50-500 per award.
Suggest edits to existing posts or tag wiki's that improve the content. Accepted edits receive +2 reputation, up to +1,000.
Join a site while having at least 200 reputation on another. This automatically earns you an association bonus of +100 reputation on the newly-joined site.