First, never trust anyone who gives you a generic answer to this question. It doesn't make sense that one thing fits everybody, anyway.
Of course all sellers will swear it is exactly their e-cigs that will suit your needs no matter who you are and how much and what kind of cigarette you are (were) using.
What may be the best e-cigarette for you really depends on what type of smoker you are. And by this I mean two things:
a) how many cigs daily you smoke
b) also important - are you more hooked on nicotine or on ritual of smoking
Thing is (a) is pretty clear to anyone, (b) not so much, I'm afraid. I don't see anybody writing or talking about it
If you are hooked on ritual of smoking, it doesn't really matter how much nicotine you take daily. In your case cig-alikes will do. And in your case suppliers' claims that their cigs are equivalent to 20 or even 30 tobacco cigs may even be true. Because if what you're missing is holding a cigarette and puffing away, it's the number of puffs that counts. (And that number is something most suppliers are telling the truth about.)
Check out my review of Apollo Extreme Kit
You may want to check out these companies and their selection of cigalikes, or as some call them - slims.
However, if you are primarily addicted to nicotine, you'll burn two, three or even more of cartomizers a day. You'll go bankrupt if you purchase cig-alikes. That's why I use them only occassionally. If this is your case too, then you might want to go with mid-size cigs.
Here's one of the most popular starter kits Apollo Endeavor Kit - click the picture to read our review. The other one that we found very satisfactory is Vapor4life Zeus Dual Mode kit - link to our review.
These were all general criteria.
Now, to the more specific ones:
There's no single answer even here. Well, especially not here, since the criteria are numerous. All we can do is name several main ones and see which brand meets the requirements.
In case you prefer pen-style cigarettes, it all depends on the e-liquid you choose.
If you want the experience that matches tobacco cigarette in your hand, Prosmoke is ideal for you. E-liquid in cartridges is pure VG, US made like everything else on that site.
When and if you want to play safe, here is Prosmoke again. It is a widely known fact that most manufacture comes from China. I myself don't really have that many concerns about it, but you might think different.
As for the e-liquid, it's Virgin Vapor, Apollo e-liquid or Halo e-liquid. The first one is pure VG.
Both these brands mentioned and reviewed in this article are regularly used in my house. You don't necessarily have to give up quality if you want to save some money.
Here you can also find what we wrote about e-cigs we liked best. Check our reviews by clicking on the thumbnails.