Not knowing anything about your cigarette habit nor how long each day you are away from power for charging, it's very difficult to make any recommendation.
In battery specs, 100mah is about 1 hour of moderate vaping with a standard resistance atomizer or cartomizer (which is all a slim ecig can use. fat battery models and various non-slim shape mods can also use the hotter low resistance parts that sue battery charger faster)
And most people here use and recommend manual batteries
And most people end up vaping with cartomizers for their favorite juices.
3-piece ecig is battery + atomizer + a stuffing and plastic cartridge aka cart (not a popular way to vape but OK for starting out) and the popular 3-pieces have cartomizers available (mainly blank cartomizers)
2-piece ecig is battery + cartomizer aka carto (a one piece disposable cart w/ internal atomizer - if you keep one damp you can get 4-7 days use or more out of one)
The most popular ecigs here
Joye 510 manual - 180mah (see Liberty-Flights.com, LiteCigUSA.net)
Joye 510 mega xl manual - 280mah but long (128mm w/ a cartomizer) (FreedomSmokeUSA and some others)
KR808D-1 manual (shorty w/ 65cm battery is 180-220mah, standard w/ 78mm battery is 280-320mah). Popular vendors are Vapor4Life for the standard style (manuals are mostly sealed, good sized button) and SmokelessImage Volt (as well as Bloogplanet Maxxfusion and Halocigs G6) are the rubberized finish style with totally sealed manuals but a very tiny button and short 5-second cutoff (but you can drag again right away)
The 510 is a 3-piece with plenty of blank cartomizers and few prefilled ones, with manuals you can use a drip tip on the atomizer to test juices, use cart on atomizer if you want, use cartomizers for your favorite thinner juices
The KR808D-1 is a 2-piece so there are a lot of prefilled cartos, a good number of blank styles of cartomizer, and to use as a 3-piece you can use a DSE901 standard resistance atomizer and carts (or drip tip if you have manual batteries)
I like both. I think 510 + Boge cartos gives a moister warm more vapory hit, and KR808D-1 give a hotter hit with more TH but maybe a bit less vapor? The KR808D-1 is 3.7v, so it runs a bit hotter than the 510. Both are 9.2 mm diameter and look thinnest in dark colors.
If you want longer battery life and the ability to get hotter hits with low resistance atomizer and cartomizers (which also use battery charge faster) then you need to skip slim ecigs and look at Liberty-Flights.com (press the 20% off upper left front page first) and then look at Ego and Riva 510. Those are the two most popular choices. beyond that are mods or many shapes (box, screwdriver shape, and more) that use removable AA-shape industrial batteries, including higher and variable voltage ones.