Christmas jewelry has a deadline and usually more than one recipient. The way to keep it from feeling like a list is to choose each piece for the person, not for the occasion.
Buy by what each of them wears. Give the mother the metal she has always worn, the daughter something she can wear every day, the friend something small enough to feel like a thought rather than a debt.
How early do I need to order?
Earlier than for any other occasion. Carriers slow down through December and delivery estimates stop being promises. Whatever window you see, add a week.
Is it strange to give several people jewelry from the same place?
Not if the pieces are chosen individually. It is strange if they are the same piece in different boxes. Different pieces, one note each, written for that person.