Here's the thing about my miniature gardens - they're easy to care for. They come with written instructions. And - you can email me if you're uncertain. Every single garden comes with care instructions. See?
I suspect overwatering is behind most cases of black thumb - in a well-meaning effort to keep plants healthy, we mistakenly drown them. Remember - most plants just want a drink, not a bath! Black thumbs can and should enjoy plants - don't let your fears keep you from taking home something like this:
Relax, enjoy and don't overwater!