I'd recommend a cheap K100 Empire clone, what really matters when you go sub-ohm is the quality of your batteries. I usually go with Efest 18650 30 amp high drain batteries. And for an rda I'd probably start with an IGO-W because first off it's cheap but it's relatively easy to build on and you have the option for single/dual/quad coil setups if you would like down the line.
i have a couple of the purple efests but i don't use them on anything lower than .6 ohm builds. if i am not mistaken they are rebranded LG 20 amp batteries. i just feel a lot better sticking to the Sony VCT5's. best of luck.