How do I get more attention on the gallery?

You'll immediately see results if you do attention grabbing thumbnails.

If you're a builder, base game builds are extremely popular, and hashtags help a lot. You can't get custom thumbnails on builds without it being marked as CC, but the best thing you could do is prioritizing the side that'll be on the thumbnail. Also make sure that your secondary thumbnails aren't obstructed by a tree.

If you're a sim creator, you'll immediately see results if you do custom thumbnails, the ones where the face takes up almost the entire frame. This tip might sound phony and you definitely don't have to do this but putting terms like "cute" "hot" "pretty" in the title usually get a lot of downloads. Also hashtags help a lot.

The most long-term way of getting attention though is collaboration. Doing other creators' challenges on the gallery will build you a loyal group of people that'll pay attention to your content. Also finding Sims communties help. The Planet Sims discord server for example has lots of people, and posting there can get you a lot of attention.

I'll make sure to check you out!