Sounds like you need a pv and cartomizers.
Here's a pic with some sizes. These are Smokeless Image ecigs but the sizes are the same as others. The two on the left are ciggish size. The three on the right are what we call ego size. The bigger ones will last longer before needing a charge.

L-R: cig, 65mm Volt 280mah, 78mm Volt 320mah, 650mah X2, 900mah X2, 1300mah X2
The small ones will give you 2-3 hours vape time before needing a recharge. Of the big ones - the first will give about 6 hours, the second about 8, and the last about 12 hours vape time. This is measured in the mah of the battery. 100mah = about 1 hour of vape time.
A cartomizer is the piece you screw on to the ecig. It contains an atomizer - which has a coil. When the coil heats up it vaporizes the juice. The filler in the cartomizer holds the juice and supplies it to the coil. Cartomizers can be refilled very easily.
So I think for starters you might want to look at what size ecig you'd like, and buy either some prefilled cartomizers or some blank cartomizers with some small bottles of different juices to try.