I have an ecig shop and website, so I get to try them all.
The ecig market has grown rapidly and development has been brisk. Recently there has been a game changer in the development of a bottom coil clearomiser, (the top bit), usually called a BCC. Most of this development has been done by the market leader, which is Kangertech.
Being Chinese, the design has been quickly copied and so some slightly cheaper copies have emerged, some branded, such as the Halo. They are not as good quality and do not work as well as the branded Kangertech.
I would advise against anything which has a "hanging wick" such as the CE4, the vivi nova, The T2 and many others. The liquid has to be wicked up to the top and, whilst they do work, They suffer from starvation and deliver more hot air than vapour which is very harsh on the throat (and make it very difficult to raise your voice pitch if you want to).
It's possible to waste an awful lot of money trying to find which is the best, so I would suggest buying the best from the start, which is IMO the Kangertech pro mini with a 2.5 ohm coil (for a standard EGO battery). You will need a variable voltage battery (ego twist is good) for a lower resistance.
Expect to pay about £14 for the pro mini but make sure it is branded Kangertech and not just Kanger which is frequently used for the knockoff's. Another good alternative which is almost as good is the Kangertech T3s around £7. (google them so you know what the real thing looks like)
I tried the Kangertech pro 2, 3, the Aerotank and the unitank and none of them are as good as the pro mini.
I get to see on a daily basis the change in people when they switch to ecigs and it's almost as dramatic as the changes with hrt.
I can understand the need for something that looks like a cigarette (like the blu), and I was the same for a few months, but you will stand a much better chance of succeeding with a proper one like the pro mini.
Unfortunately if you go to a local ecig shop they will try and sell you what they have a lot of and will tell you it's the best. Know what you want before you go.
Amazon won't allow cigarette as a search term but if you put in Kangertech as a search you have a good choice.