Generally It takes 60 votes if it a bill can’t pay for itself. It appears the budget is a different beast and just needs a simple majority since it’s guiding how the money should be spent. The only thing is that it can require 50 hours of debate. They can probably do continuous 50 hours. Shut down Saturday at 12:01am and reopen Sunday evening or Christmas Eve morning after 51 votes. POTUS already issued EO declaring an extra holiday for Christmas Eve. A shutdown through Christmas Day is a nothing burger.
https://www.politifact.com/truth-o-meter/statements/2012/feb/13/jack-lew/white-house-chief-staff-jack-lew-says-budget-requi/