If this is a route you want to pursue, there's a progression you have to go through. Remember, you had to crawl before you learned to walk.
You already have a K100, you'll need a RDA, I would highly recomend one that had adjustable airflow and allows you to build single and dual coils, you'll need wome Kanthal resistance wire, best to get is 28 & 30, they are the most versatile and 30 is a very easy wire to work with, so it's easy to learn with, you'll need a multimeter, this is crucial! You need something to moniter the remaining charge on your batteries and you need to check and recheck your resistance.
Start slow, what I mean by that is practice! Try building to around 1.5 ohms consistantly before you move to anything else. It's a good resistance for a single coil and is a lot more forgiving on your batteries than anything lower.
There is a lot more, but it comes from familiarization with your equipment and experience.
and last but not least, READ, ReaD and read some more