Sub-Ohm Starter Kits - Starter Kits
A sub-ohm kit is a mod and a tank sold together, already matched, so you are not guessing whether a coil fits. It is the step up from a pod system: bigger battery, bigger clouds, more to adjust.
What to look at first is battery. An internal-battery kit like the Geek Vape Aegis Boost III charges over USB and that is that. A removable-battery kit like the Smok Mag Solo or the Smok Morph 3 takes 18650 or 21700 cells, which means you can swap in a charged pair rather than wait. The Vaporesso Gen 200 with iTank 2 is the long-running favorite in that group.
Whatever you pick, buy coils for it at the same time: a kit ships with one or two and they are a wear part. They are on pods and coils. If the kit takes removable cells you will also want 18650 batteries and an external charger, which is safer and kinder to the cells than charging in the device.