Additional details of question
I’m looking to update the design of my Weebly website so that it looks nice for mobile viewing. Should I buy a custom Weebly theme or update one of the existing Weebly themes?
A problem that we hear about with Weebly websites is that people aren’t confident to update the design themselves and “build” a more modern Weebly theme using the free Weebly theme options. In all honesty, more than half the current Weebly themes look dated and wouldn’t work for a professional business website.
If you’re looking for a Weebly theme that is mobile-responsive, I’d recommend looking through their theme options, previewing themes, selecting a theme, selecting mobile view and then changing to a different theme if you don’t like the pre-configured mobile options.
Another big consideration that I need to mention is the typography & colour scheme of your Weebly site. I’d recommend that you look into sites that help you pair fonts , find font combinations and choose colour combinations that suit your branding. Pairing a clean theme, colour, typography and beautiful stock photos will take you a long way towards a more modern Weebly website design.