Lots of different ways to go.
I like the Carvin plastic power speakers. I have the 15" 2-ways, and you could do a small solo gig with just that. If you are doing a duo or trio though, I would go with a top box mixer-amp and a pair of speakers on stands. Carvin, Mackie, Peavey, Yamaha all have good systems. I would want at least six channels, but eight is better. On a tight budget a used PV XR-series top box is hard to beat. I have an old XR-600C, and it still works great. And with the mixer amps, you'll get some effects and a graphic for feedback and tone control.
If you go with a top box you'll need non-powered speakers. I like the plastic ones. They don't sound as good, especially at high dB levels, but they save a tremendous amount of weight. I like the Carvin and Peavey offerings. Mackie is very good but more money. Carvin makes a 15" 3-way, and that is a terrific speaker for acoustic instruments.
I would avoid the small systems like the Fender Passports...PV has one too. What you really want is some modularity so you can expand your system over time as your needs change. It may cost a little more to start, but in the end it could save you big bucks.
Good luck.
Bill