Ugh there are so many variables to this question, it will be hard to answer. When building dual coils, keep in mind that the resistance will be half of both coils added up. So say you build both coils at 3.0 ohms, your resistance will be 1.5 ohms. Depending on what device you are using your igo on, most VV/VW mods do not fire underneath 1.2/1.3 Ohms, so 1.5 would be a good starting point.
As far as what resistance wire would be best, 32 or 34 should get you close. Anything above that, the wires get too thin.
I would recommend you try simply building a working single coil first before attempting a dual coil setup. I haven't seen much as far as videos that get into rebuilding the IGO W, but I have seen a ton with the IGO-L. I would say maybe watch some of those and watch some more videos that are building dual coil setups of different brands.
Given that you are so new to RDAs, I think you should do a lot more research before attempting to build your own. Lastly, ALWAYS CHECK YOUR RESISTANCE BEFORE FIRING ON A MOD! Get a multimeter, ohms meter, or use aa mod that checks resistances.