What size feeders to buy?

So Ari is currently 250 grams, so she should be eating rats between 25 and 35 grams. I have five rat pups left that are between 20 and 30 grams--so they'll work for now. Ari's been growing at about 50 grams per month. The question though is what size feeders should I get from the expo this weekend? If, by the time I run out of rat pups, she'll most likely be 300 grams, and eating between 30 and 45 grams/meal should I buy like 5 of that size, 5 of the next size, 5 of the next and so on?

How do people generally buy frozen feeders for a single young and still growing snake?

(Ari was hatched in the beginning of May)

(also, at 26 inches is 250 grams a healthy size)

Oooh, it actually seems like Ari's growth rate is very slow. . .so I'll be going back to feeding every 4 or 5 days rather than every 7. Hopefully that helps get her on track!