Welcome to the Forum! You will find a wealth of information which at times may seem a little overwhelming, but the important fact is that you made the first step! I personally have only tried the Blu disposables but they were good and got me through a long weekend without going back to tobacco cigarettes.
Just from information others have posted here about the Blu system, it can become expensive buying the prefilled cartridges, but the good thing is that they are readily available in any pinch. I know that Johnson's Creek makes the liquids which are used in Blu ecigs.
Johnson Creek Smoke Juice - America's Smoke Juice! Johnson Creek Smoke Juice
But I also know that the tobacco flavor is the Blu is specifically for the Blu...but if you like it then you might like the other flavors too. You can buy the juice and refill the cartos (cartridges) and they will last you longer.
There are so many choices, and I am sure others will chime in soon. Just take your time and enjoy the vape...and read, read, read.