I recommend starting with the Igo-L first. It only has 2 posts (1 + and 1 -) unlike the others which have 3-5 posts for your bigger builds such as a quad(4) coil. And even though the Igo-L only has 2 posts you can still have a dual(2) coil duild. I learned on the Igo-L first and then bought the W, and now I use the S. So start small, and work your way up.
All these IGO-L fans lol really the IGO-W is easier to build it's got wholes through the posts also it has the advantage that you can just build single or dual, quad. It's one hell of a dripper bored out to 2mm and running 0.8 - 1.0 ohms it chucks out plumes on heavy VG juice, had it at 0.6ohm for #VapeMeet, then if you really want to play the new IGO-W3 which is quad but is a fiddly build but when get it working it's a beast!