the local business redesign angle is solid but i'd add one thing... dont just redesign random places, pick ones in the niche you actually want clients in. if you wanna do restaurants, redo 3 restaurant sites. that way your portfolio reads as specialist not generalist and people pay more for that.
free work i'm mixed on. it works but only if you set boundaries first, like one revision round, clear scope. otherwise yeah it turns into the nightmare clients everyone warns about. the testimonial isnt worth a month of unpaid edits.
also dribbble is fine for showing work but it wont get you clients on its own, nobody hires off a dribbble shot alone. you still need an actual page where the work tells a story... problem, what you did, result. even if the result is made up for the concept ones just frame it as "concept" honestly.