Yikes.....

Ok, getting a little overwhelmed here. I just recently started dental assisting school and currently have one instructor that is highly allergic to cigarette smoke and I know that when it is time for us to do our clinicals that the odor would be a big draw back as well. Thus the interest in trying ecigs. Over the last few days, I have looked at soooooooooo many sites and soooooooo much information I am totally lost and really want to scream. We have order a couple of trial versions (Prada and directecig.com) and needless to say we will look at the fine print when they arrive!! If it looks like extra charges will come they will get shipped right back....without me even trying them. I currently smoke Misty Silver and Capri Jade (yeah, two brands...one is cheaper than the other and there is a size difference as well). I am concerned, though, that the lower cost "free trial" versions will not perform as well as some of the regular models and that will turn me off of it completely. I am lost as to the battery/atomizer ratio. I know that they effect vapor production. I do want a good easy pull with the solid feeling of the smoke (vapor) hitting my throat. Cartridges are a complete loss to me and what is with this "e-juice". Do I have to mix this myself or can I buy it premixed. On the hardware side of the models, what model parts interchange with other model/brands parts? Now you can see my confusion. I am hoping and praying that there will be somebody here who can help me out with getting all of this straight without them having their bottom line (profits) in mind.  Thanks