While you do mention the stage size, you have to know that the stage size is meaningless unless you just want that sound system to be heard by the person on the stage.
What matters is the audience, and where they will be, and how much volume you need.
Lightweight means... light on everything. You can't get big sound with light gear. Amplifiers have heft and weight. Bigger speakers have heft and weight. Durability adds heft and weight.
and cost
You also need to consider whether a single speaker at the front of the space makes the most sense, or if you want to put a speaker on both sides of a speaker and wire the two speakers together for more even audio coverage.
A pretty basic wired microphone is the most reliable solution. It is cheaper than quality wireless mics and works well. Like a SM58 from Shure.
I do like QSC as a bit better audio quality for the money spent, but mostly a PA speaker would be what is used.