I think it's worth joining a signature campaign even if you're a newbie just don't randomly spam across the forum like others have been saying. Even though the earnings aren't much, small earnings are better than no earnings. Regardless if you're in a signature campaign or not it should always be you're goal to increase the value of content on the forum.
It really depends some levels are just so little it's honestly better off learning about the forum, and how to make constructive posts. You are judged at a different level on quality of posts once you add a signature.
I'm assuming person is new to site. It takes a little time to learn about BTC and be useful for giving advice. Sure some who are new are not really new who might be able to jump right in. It is sad but a lot of the new people who jump straight to sig campaigns start to only worry about post counts.... then this is where bans come into place.
The pay is so many times better once you reach full member missing those lower levels really will not matter in scheme of things.