A Secret Santa list that keeps the budget and drops the guessing
Secret Santa fails in the same two ways every year: somebody blows the budget, and somebody gets a novelty mug. Both are guessing problems, and a short list of things you would actually keep solves them.
Put the budget in the list
Name the list for the cap — "Secret Santa, £15 max" — and only add things inside it. Your Santa then has three or four real options and no risk of overshooting, which is the thing people are most anxious about.
Three or four items is the right length. A list of twenty defeats the point and reads as a shopping order.
Where the secrecy actually sits
Be clear on how this works here. When somebody reserves a gift, other visitors see a first name so two people do not buy the same thing. Your Santa can simply type a nickname instead — "your Santa" does the job — and stays anonymous.
What is guaranteed is that you, the person the list belongs to, never see any of it. Not the name, not which gift. That is enforced on our side, not left to good manners.
One link for the whole group
Everyone in the group makes their own list and shares their own link, which means the organiser never becomes the person collecting preferences by message. Pairings still happen however you already do them; this only replaces the guessing.
Will my Santa be revealed?
Not to you. Reservations are always hidden from the person whose list it is. Other visitors see the name typed at reservation, so a Santa who wants to stay hidden from them too can use a nickname.
How do I keep everyone to the budget?
Put the cap in the list name and only add items under it. The list itself becomes the limit, which is easier than policing it afterwards.
Does everyone need an account?
Only to make a list. Reserving needs nothing at all, so a colleague can pick a gift from their phone in thirty seconds.
Can I use it for a family draw rather than an office one?
Yes, and it works better there. Family draws usually span more ages and more distance, which is exactly when guessing goes wrong.