gary:

I'm starting mine out in 3 gal and planning to try staying there until it doesn't work. I've had up to 18 lbs fruit from a 15 gal size pot. But that's near 100 lbs even with a light media. Too much for my aging back.

Waiting,

Yes a gallon size pot to start should be fine. Some of the commercial blueberry growers here grow mature plants in 25 gallon pots. The bigger pots are better as it makes the plant more stable and helps to keep the media from over heating in the summer sun. Fruitnut growing his in a greenhouse avoids a lot of those problems.