Plain wire for a start, perhaps between 28ga and 26ga. I like 27ga and 26ga thickness, but some people find that too thick and swear by 30ga. I don’t recommend 30ga to start with, it’s thin and difficult to work with.
I also don’t recommend MTL Clapton or MTL Fused Clapton for beginners, if you get into building then you’ll try them out if you’re interested.
Materials:
It doesn’t matter which one you get… To each their own, you have to try them out. I like Ni80, but many people here use A1. I used that to start too, but I didn’t like that it was “sluggish” with larger coils; however, with MTL, this problem doesn’t exist. Furthermore, I think Ni80 is slightly better for my fruity juices… It’s like it brings out the “high” notes better, like citrus, while A1 is better for mid-low flavors (nuts, cookies, tobacco, bean stew) - but this is just my humble opinion, it could also be a placebo effect…
I don’t like SS because its resistance is low, and you can also taste a metallic flavor (which you get used to within a day, to the point where you don’t notice it afterward).
Cotton… It doesn’t matter at all, as long as you know how to cut it to the right size if you buy something like Muji pads.
If you don’t want to bother with cutting and fluffing, then I recommend 2.5mm BP for its good value.
I’m a fan of Muji pads, mostly for “nostalgia” reasons, but out of laziness, I’ve used a lot of BP.