Yes... a stereo out can run to one speaker... Some boards have a 1/4 Inch out, and others use XLR (mic) cables. XLR cables are best for long cable runs. We run one output cable from the mixer to the left hand
main speaker, and then run a cable from that to the right main speaker, across the fromt of the stage.
I use something similar to what was described above...
a 10 Channel Soundcraft mixer, and four powered speakers. 10 channels is barely enough for my trio,
because we each use several channels. We use this PA for gigs where they pay us extra if we bring our
own sound. We mix from the stage, so we have no sound man, no snake, and sound check takes at least an hour, depending on the room or the surroundings. The Soundcraft mixer has a separate monitor mix and
output, which is very handy.
I wouldn't waste your money on cheap equipment. Get the best you can afford, because it will serve
you better, and you can actually sell it if you change your mind about your requirements. If you buy
cheap equipment, no one will buy it once your realize it won't cut the mustard. Soundcraft mixer seems
like a moderately priced unit.
https://www.sweetwater.com/store/search.php?s=Soundcraft+mixer
I had to spend a weekend reading the manual and plugging things in and out in order to learn how
to use the new Soundcraft board. But it was worth it. It has great features. The sound craft signature 10
is actually an old fashioned mixer, because it has real knobs... Lots of groups control it all with an iPad.
If you're feeling modernistic, that might be the way to go. My group bought the older style because
we're effing old... and we didn't trust all that invisible technology. *shrugs.
Speakers is another can of worms. Some are good, some are not. Often you get what you pay for.
My group uses Harbinger speakers, which are in the "inexpensive" category, we pounced when we saw
them go on sale. Lots of members will have their favorites. Peavey is always good IMHO, as is JBL.
Good luck with your quest.