I'm currently on less than 1/10th of an acre and there's plenty I can do here, and I'm pretty content with what I have
Time is still more of a limitation than space to what I can produce.
We grow a dozen different types of fruit
trees and shrubs, a full
medicinal and tea garden, perrenial vegetables, a couple of areas for annual veggies (even though that's not my strength). Even the top of my shed is used for Boston Ivy, which I use for basketry. In a small lot, everything is an "edge" and
permaculture thrives on edges.
I still see a bunch of places and think "wait, with the right system I could grow something there". There's the
mushroom logs I want to put in the full shade area, my daughter's balcony that would be great if I can figure out how to
water things up there, the neighbours'
fence that would just be perfect for beans, the little corner where I could raise quails...
I can't really do grains on a large scale, or large amounts of storage staples like potatoes. But those are easy to get from organic farmers.