1 or 2 gallons. Sometimes do the parti-gyle thing, which usually winds up being 3 1/2 gallons total.
I keep it small because I like to brew once a week when time permits, I enjoy the experimentation and variety. I work stovetop, indoors, using two commercial stock pots, a colander, and I keep two tea kettles full and on medium heat. But I should add that at these low volumes, my most important tools are my calculator, pencil, and electronic kitchen scale.
Tried a "big" batch once but didn't care for it. By staying small, the Heating, chilling, pre-clean/san and clean up all seem to go faster for me. Then all the follow up operations, bottling, etc. all go faster. The other nice thing is I can ferment/secondary/age in a couple of one gallon containers. I use a mix of plastic milk jugs and homer buckets. I tend to toss out (recycling) the plastic milk jugs rather than try to clean out the fermenter funk.
It's ghetto, but it works for me. No heavy lifting required