If you know these users you could stub out the pages and features for each user and then create roles that let them edit the pages and/or create new pages.
However the blog does not have a built in gallery, those are separate features. They can post images directly in a blog or they can add them to galleries and then link to the gallery from the blog. The blog also does not have sections, it is like all features it plugs into a cms page and it has some supporting pages it links to but they are not cms pages and pages cannot be added to the blog other than blog posts. You can create child pages beneath the cms page that contains the blog.
Hope it helps,