I started with a small flock, small coop... at least I had the foresight to build a very large run in comparison (though was using half of it for gardening).
After 2 years we had a larger coop built (going from 16 to 60 sq ft) and now my garden is on the other side of the yard, freeing up the entire run space.  My plan is to have up to 12 birds but to get there slowly, as I don't plan on culling retired layers, so we're only planning to add chicks when egg production tapers.
I waited 30 years to get chickens so I'm in no hurry to max out the flock, especially when we can only eat so many eggs...