If you're okay with something that doesn't look much like a cigarette, and has a manual button (push to vape), the Riva 510s are indeed attractively priced. Liberty Flights has an ongoing discount code (october20) that gets 20% off, their Riva basic kit (2 batteries, charger, couple atomizers and cartridges) ends up being just over $30. LF shipping is also pretty cheap.
I strongly recommend the Boge 2 ohm (LR, low resistance) cartomizers, available from LF and many other places. They're good to use on the Riva, though not on the smaller 510 batteries.
If you prefer cigarette form factor, including a light on the end, KR808D-1 XL (or mega) batteries are probably where it's at.
I ran about 3 hours per 808 standard 280 mAh battery, 4-1/2 on an 808 XL 380 mAh, 8 hours on a Riva 750 mAh. Everyone's mileage varies, depends on how often they vape, resistance used, etc.