It's really confusing at first, but you'll need to figure out how you'll be using it.
It depends on how you'll be using it and what you consider more convenient for you. Typically most people start with the ecigs that look like actual cigarettes. But their battery life is bad, and you're probably going to use catridges. If you don't mind using a bigger battery for performance the Ego-C Twist is pretty much the standard for beginners and is really good and the 1000 mAh Ego-C Twist will probably last you all day.
Now there are a few juice delivery systems, there are atomizers, cartomizers, clearomizers and tanks. Atomizers require you to drip drops of ejuice regularly. Cartomizers are like the ecig cartridges for blue, they can be refilled and used many times. Tanks are what goes around a cartomizer, it allows it to hold more juice and stay saturated better. Clearomizers are like a tank and cartomizer system but they're mostly all one piece and some even have replaceable parts.
Just keep looking around and try to absorb all the information, you'll understand it. Also if you have a vaper store located close by it's nice to go check it out and familiarize yourself a little better.