The best mod is a self made mod. If there is any useful advice to give anyone on these forums, it's DON'T NEGLECT THE MODDERS SECTION OF THIS SITE.
When I first got into vaping, I wanted everything! I didn't care about anyone's recommendations. I know very well, opinions vary and often times, the opinion is not mutual.
So I bought several ecig models at one time, found that they all require different techniques to achieve similar sensations from one to the other. Some required more finagling than I had the patience for.
I was often directed to these commercial mods, but always hesitant on purchasing since I'm not fond of my PV looking like an adult toy.......near my mouth.
Then I decided to explore the modders section of this site.
There are so many tutorials, people willing to help and useful info, that it's rediculous to not take advantage of the resources available to you.
Soon after, I learned that all these mods....were in my ability to do. I could even replicate these commercial mods, since many of them were the back end of a flashlight, cut up BBQ grill lighter, etc.
So, I figured...before I invest money into something that isn't really original to begin with, other than the idea. Let me see if I can do it.
Your own USB passthru, is a good starter...than the Nicostick, very good stepping stone to portable pv's. Maddogs flashlight mod, next step. Thereafter, you should have been inspired enough to envision many possibilities with in your grasp outside of tutorials.
The investment is very minimal, and skill requirement is minimal. All you really need is patience and perseverance.
It pays for itself in the long run. You might spend 30 bucks for tools, supplies, and parts in the beginning...but after that, you can make however many you want at a very low cost.
Imagine only having to buy attys for the model you would like to try. No need to buy an entire kit, unless you want to.
Just my 2 cents. Let the prodigy, screwdriver, and so forth recommendations continue.