You have to inspect the inside surface of the tire carefully for intrusions of wires, thorns, and the like. Sometimes you can't see it initially but can feel it by running your fingers over the interior. Also you have to inspect your rim strip or tape because during installation of a tire the rim strip or tape will move laterally exposing the tube to a sharp spoke hole edge or nipple. In my experience rim tape works a LOT better than rim strips. Also you should use fine sandpaper or a micro-file to round-over the valve hole edge which is often is sharp enough to cut through the tube eventually. I try to avoid ultra-light inner tubes because in my experience they're a lot more prone to failure. 80-90 gram tubes are better than 60-70 gram tubes. Lastly, some tires puncture a lot more easily than others. People love the Continental GP4000S2 because they resist punctures yet are lightweight. They have a built-in puncture-resistant belt made from Kevlar under the tread. You probably have a combination of all these factors contributing to your frustration.