I strongly recommend watching videos about RDA's on youtube. They will help give you a good idea of what might work best for you before you spend your money, and will also give you a lot of necessary information about battery safety, as well as all the options available to you. Check out Grimm Green's channel in particular for literally dozens of videos on the subject.
As for me, personally, I mainly use two drippers now - the Jam clone, and the CLT by Infinite (you can check out my blog here on ECF for my reviews of these items). They both have their ups and downs, but work great for my style of vaping. And yes, they will work on any device as long as you build your coils to the appropriate resistance. Check your iStick's resistance limitations, and go from there. I started with a simple dual coil setup on a dirt-cheap Nimbus clone, but newer drippers have many more options to tailor your vape, like adjustable airflow and the ability to use either single or dual coils.
Good luck and vape on!