No to gloves on an idiot string.
No hat under the helmet, just a warm fleece or woolly one for when he's not wearing the helmet.
3 pairs of ski socks should be fine, and unless there are freak weather conditions he shouldn't need to wear more than one pair. I don't suppose he will give them a quick wash at the end of the day? He can wear each pair for two days otherwise, but needs to hang them out over a radiator or something to make sure they're not damp.
Working from the inside out he needs thermal top and leggings with long sleeves and high neck. Possibly a t shirt or two if it's very cold, thin but warm fleece with high neck, ski jacket and ski trousers. Gloves, socks, hat, some sort of waterproof boots. Goggles or glasses. (You don't need expensive thermals or fleeces, the lower priced ones are fine).
It can get expensive, so borrow as much as you can from friends if that's possible, just in case he never goes again.
We find tog24 excellent. There is an outlet store near us, and the prices are good. The clothes are good quality but without a ridiculously expensive designer label.
I would buy a jacket that he is happy to wear as a normal winter coat, not just a special coat for skiing only.
Don't buy a helmet, that will be hired at the resort.
I find mittens warmer and more comfy than gloves, but my kids prefer gloves. You can get very thin glove liners that my DD (16) wears, but she tends to feel the cold more, and I've certainly never needed them, I find ski gloves/mittens are wonderful these days.
Scarves are not recommended for skiing, but I have a sort of thin fleece tube thing which I love. I wear it around my neck and it fills that gap between jacket and helmet. You can pull them up over the face if it's windy, great on the chair lifts.
He also needs high altitude face cream to stop him burning, and lip protection. You can usually get a little two in one set, they're not expensive.