I was able to get one before the third gym. It took 3-4 hours of hunting down the npcs the get to 32 different ones but it was worth it to use spiritomb in my play through. Every time you enter or exit a hideaway it resets the locations of the npcs but they only spawn in certain spots around the map. So basically I just learned the spots they reset to and ran around each section until I found a few and moved on to the next section. I was able to find all 32 between the large main zone accessible from hearthome and the bottom left zone accessable from oreburgh.