Breast milk storage?

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Help! 36w FTM, I'm trying to get my last things in order before baby gets here. I plan on EBF, but I have a double breast pump from Bellema as well. It only came with 2 bottles, and I'm not sure what to use as storage. Can I use any bottles? Or should I get bags for the breast milk? What's the best brand? 
They seem sooo expensive to me! 
Please help 😞