Starter kit/batteries I used for close to a year when I started vaping was the Kgo kit from Hoosierecig. It's updated now with 1300Mah batteries but I haven't tried the new EVODs the kits come with. I've enjoyed Kgo batteries with a slim Smoketech dual coil cartomizer tanks. Far as batteries go the Kgos are good bang for the buck. Size compared to battery life good. Recommend lower 1.5 -1.7 ohm type devices as they are set for 3.7v. (So lower Ohm/resistance give little more power to attached device)
If you want to try adjustable voltage is small package there are some Vision spinner 1300mah kits. Depending on where get get them the attached atomizer device maybe different. They are good little batteries that give you an adjustable 3.3 - 4.8v. Just slightly longer than the Kgo megas 1300mah.
If you want something bigger, better battery life, and variable volt look at the iTaste MVP kits. It has internal Battery and charges like a phone. Believe its 2600mah. The iclears 30/16 that come with different kits are good beginner vaper devices. iTaste VTR, which uses external batteries, also comes in different kits with iclears. Just make sure the kit either says 18650 batteries/charger included or gives option as an accessory addon. Batteries that work well in these external battery type devices: AW IMR 18650 2000mah, EFEST IMR 18650 2000mah, EH 18650 IMR 2000mah.
Although I've never tried one, the protank II also seems to be a good device for most beginner vapers.
I've been making my own juice, so I'll let one with more experience on different vendors give ya some suggestions.
Also, check out these youtubers
GrimmGreen
Pbasardo
Todd Ecigreviews
Rip trippers
Those channels has tons of good info. Hope that helps.