You can try the Suppress from Latest plugin, it would help here, you can also mute that category for all users, so they don’t get notifications or see the category as they use the community. This post explains in detail the difference between the 2 features I mentioned above.
You should be able to adjust the Trust Level settings such that users need less topics entered and posts read to get to each Trust Level? You can search for requires topics in the Admin Settings, and look in the Trust Level section (/admin/site_settings/category/trust) to see the relevant settings.