You'll need to assess some things. How much money are you willing to invest initially? Does the size of the device matter to you? (In general, larger devices perform better). How much time are you willing to invest in a learning curve? Do you enjoy tinkering, or are you more a "set it and forget it" kind of person.
The one thing that I would say as a blanket statement is, unless there is an overwhelming need to look like you're smoking, avoid anything that looks like a cigarette. Batteries with a capacity of less than about 650mah, have severe limitations imposed by physics that no manufacturer or fancy looking package can overcome. Fortunately, there is a large selection of devices with larger batteries, both sealed within the device, and separate (like a flashlight). When you hear someone refer to a "mod", they're talking about the latter, i.e., an e-cig that takes one or more separate rechargeable batteries.
The "mod" class of e-cigs are the best performing and most versatile types. Most come with a "510" connector, which refers to the threading pattern, so that any 510 cartomizer (cartridge) or other device will fit an e-cig with a 510 connector.
Beyond that, it's mostly a matter of your budget. Allocate funds for consumable extras like atomizers, cartomizers, batteries and e-juice. Once you have a device, your biggest expense will probably be the e-juice, unless you like to experiment with all the latest and greatest cartomizers and tanks, etc.
If you want an "Industrial" duty starter kit, you need something capable of putting out at least 3.7V for a sustained length of time. That means a battery with a min. of about 900-1100mah. Once you have that, it's a matter of what cartomizer, or other device, you put on the end of it.
If your budget for a device, including a charger, batteries and a couple months worth of supplies, is less than $100, look into something like a kGo or e-Power or Lavatube (sold under many different names). The Lavatube is a variable voltage device that will allow you to tailor your vapor more to your own tastes without having to use cartomizers of differing resistances.
For $100-200, the field opens up and includes some very high quality fixed voltage devices and a couple decent variable voltage ones. Contenders would include the Silver Bullet, GPV, GG for fixed voltage and the Vmax and BuzzPro for variable voltage.
Over $200, you're into the range of the Provari, Darwin and the best of the best fixed voltage devices like the Reo.
Every one of these devices would be more than adequate to put out some industrial grade vapor. The differences are in build quality, versatility and aesthetics.
