"wholesale" is called 도매. So wholesale business is 도매업, and wholesaler 도매업자. But these are business terms. Consumers usually can't buy directly from them unless they are buying in a really large quantity. For buying something in bulk, you can search for 대량 주문 (ordering in bulk) or 대량 구매(buying in bulk quantity). "Discount for bulk purchase" would be 대량 구매 할인. For "bulk quantities of skincare ingredients", you can search for "피부화장제 대량 구매 (방법)" = (How to) buy skincare products(피부화장제) in bulk quantity.

I'm not sure I understand.. just try to search for 화장품 세트 or 화장품 대량 or 화장품 대용량