Should I use a theme? I'm very sorry for this basic question but I'm new to WP. I just watched one of your YT vids on Gutenberg and I'm trying to figure out what to do with my site. So is Gutenberg something I should use WITH a theme or should I use Gutenberg to build my own thing?
Gutenberg is a content builder, it will only help you layout your content for a post or page. You will still need a WordPress theme for your site. I recommend the Astra theme which is free and has full Gutenberg integration.