+1. The eGo One and the iJust2 are as good as it gets for moderate cloud with (sort of) small and inexpensive gear. If you want big cloud, you're looking a a minimum of $100~125 for gear, plus some time (and money) spent acquiring coil tools and parts and learning to use them. In that price range you can buy a Reauleaux RX200, 3 Sony VTC4 batteries, a Nitecore intellicharger or Xtar 4-bay charger, and a Mutation V4 RDA. A few bucks more will buy a couple of spools of wire and some wick material. A coil tool will run $3-40, depending on what you want, and a coil too kit with pliers and tweezers and an ohmmeter--you really do need an ohmmeter-- 50 bucks and up. For juice, if all you want is cloud, I'd recommend straight VG. You can get a small bottle--3-4fl oz-- under 5 bucks at chain drug stores or Walmart. This rig will be much larger and heavier than a vape pen although, oddly enough, shorter.
If you want more than that, the price goes up. Way up. Fast. For example, a Kennedy Competition V4 RDA is over 100 bucks by itself.