Theme recommendations needed

Hello, newbie here. My wife and I are setting up a blog, and I'm looking for a specific kind of theme, but because of our lack of experience I'm not having much success finding it.

Basically, I need a theme that does the following:

• Displays blog posts as tiles/pics with captions
• User can filter by specific topic/tag, so if I want to see only travel related posts, only tiles with that topic or tag will be displayed
• Works well on mobiles
• Is reasonably easy for an inexperienced user to edit/adjust

How/where should I look for a theme like this? Or can anyone recommend one?

We don't mind paying for such a theme, but as at the moment we're working on this as just a proof of concept, we would prefer it to be not too expensive or even free (although aware that support would be not available in the latter case).

Thanks!