Congrats on your mommyhood :)
You have a couple of options.
First, please do not use water bottles. Those are single use only and leach icky stuffs.
You can certainly buy 4oz bottles and reuse them. There are some breast pumps that attach directly to bottles and you can use a closed cap (no nipple) to store them in the freezer or fridge. This can be very convenient
If you are using the "baggy bottle", you know, the ones with the plastic liner -- I do not know their official name -- you can actually get zip-seal baggies that fit the bottles and store your breast milk directly the bag and have it ready for use.
Ziplock baggies work for some moms. Really, any sealable container that is freezer proof and can stand a warm water bath is all you need. Small mason jars (1/2 pint)…whatever works best for you and is intended for reuse (not single use like water bottles).
Do not, however, layer your milk. This method, where you take fresh milk and layer it onto frozen or chilled milk can actually spoil the breast milk because it effectively promotes microbial growth by “thawing and refreezing”.
Hope this helps…