I don't have a feeder city and my storage is currently at 330. With 1 more lock to get it to 340. I am shooting to get to 500 and then can focus on other things.
All l do is go to HQ and if an item I want is for sale great I tap on it, if there is nothing there I go to any city sometimes I get lucky and an item is there. Then I look around for the blue bubbles and tap those and I either have something I can sell or its something I need .
it can be tedious but it will be worth it once I max out my staorage. Then will get back to playing the mayors contest.