Well, a lot of it is what are you looking for in an ecig? If easy, close to a traditional cigarette, down and dirty, then I'd hugely recommend the Halo G6 kit, which for $44.99 will blow the socks off blu both in terms of quality, battery life,and overall
vaping satisfaction. You can start off as simple as you like, with pre-filled cartomizers, or you can progress to re-filling your own (more economical and better variety of flavor). Halo makes a darn good product and has very high quality, tasty
ejuice flavors.
The problem however with all small, cigarette-sized batteries, even the best of them, is that you can only pack so much power in a small battery. Many, if not most vapers quickly move on to a larger battery and find clearomizers much better than the pre-filled cartomizers.
A better starting point would be at least an eGo style battery/clearomizer combination. Much stronger vape (smoke) and decent battery life.
You will hear many here talking about a vv or variable-voltage eGo type battery. Sounds complicated, but it simply lets you adjust the battery output to tailor the strength of the vapor/flavor to what works best for you, so don't let variable voltage scare you off!
Personally, I do
not recommend drug-store/gas station disposables such as Njoy, blu, etc. Most of them taste mediocre to nasty, and often crap out in a fraction of the time that they claim to last...they have turned off many a prospective ecig user.
Like I said, if you simply want a basic, small, cigarette-replacement with minimal investment of either money, or "learning", check out the Halo G6. If you aren't afraid to dive in a little and get something that will carry you a bit further, go for an eGo style battery/clearomizer combo. If you
really want a reasonable size (the same as an eGo vv) ecig with maximum features and flexibility, then I'd strongly recommend an Innokin iTaste 3.0.
PS - You are already off to a far better start than I had by asking questions in this forum! I would hate to tell you how much money I wasted buying mediocre to downright crappy ecig kits! Blu at least uses a good quality, tasty ejuice...but it all goes down-hill from there. Some of the worst-performing batteries in the industry, and refill cartomizers are too expensive. You can pay less and yet do much better.