I'm going to a expo to collect my snake, a 275g male, and it's food. It's on pinkies now. But how much do I need to stack up on? I have no seller near me(in my little Swedish town).

I pre-ordered 10 pinkies + 20 fuzzies + 10 x 30-60g rats, and five newborn chickens.

I want food for atleast 6 months, and obviously I will consider the snakes size and growth when feeding, but in your experience, what do I need to stack up on? I know of the girth rule and the 15-20% rule, but I have no idea how quick snakes grow.