What mod are you going to fire the rda with.
Without going crazy you can do a dual coil at 1 ohm, Each coil would be 2 ohms 28 gauge kanthal cotton wick. Use a 100% VG base e liquid.
Now if you want real big clouds, Big air holes and sub ohm builds will get you there. Zero nicotine and 100% VG liquid.
Are your battery's up to the task of going sub ohm? 30amp IMR's like Sony VTC4 or 5's, Efest purple, LG 30 amp
Before you jump into the sub ohm world you'll need to understand ohm's law. Or at least have a site to check your ohms against the amp draw under load the battery's will see. Here is one for you http://www.steam-engine.org/#main
Plenty of videos on sub ohm coil building out on you-tube