What builds have you tried so far? How did you feel about them?
Regardless, I would say to start simple. Dual coils and dual parallels work well. I spent all night doing a quad build and didn't like it one bit better than my dual parallel builds. I don't have any experience with the iStick 50 but you might want to try 26ga macro coils, 8-10 wraps. Always cranked to 50w. I use an 1/8" drill bit to wrap around most of the time. It makes for a coil that is easy to wick, but there's a thousand ways to wrap and wick a coil. 28ga parallel coils might produce more vapor but they won't be as easy to wrap.
Your mod limits you a little. A mechanical mod might open up your options to include 26ga parallel coils (one of my favorites for clouds and flavor). They usually clock in at just under 0.2 ohms though. Something to consider down the road.
I use
http://www.steam-engine.org/coil.asp to see how many wraps I need. Make sure to input all of the data correctly (gauge of wire, diameter, desired resistance). There's a option for metric or standard depending on which you are more comfortable with. If you get to playing with the calculator see if you can get the "heat flux" up and the "heat capacity" down, as a general rule. I open new tabs in my browser so I can compare two or more coil setups.
As usual I might have just muddied the waters instead of helping.
Good luck!
