Originally Answered: What kind of formula do I buy !?!?
It really makes no difference. All formulas must comply with certain guidelines for nutrition. The only difference may be in texture, price, organic/not organic, or added DHA/ARA.
If you don't care whether it's organic or not, then pick whatever is cheapest. Regardless of price, it still has to comply with those guidelines, so it makes no difference.
The DHA/ARA they add to formula, infant cereals, and baby food is not the same as the DHA/ARA found in breastmilk. The companies derive the DHA/ARA from algae, which has gotten some babies quite sick. And there's been no benefit shown from adding these compounds, probably because they're derived from algae, instead of coming from breastmilk.
Personally, I'd change your plan and just stick to breastfeeding for the following reasons:
~It's way healthier.
~Exclusively breastfed babies can't get constipated...constipation is an issue with many formula fed babies.
~Breastmilk is fre.
~No bottles to wash or heat up, no formula to mix.
~Breastmilk will always be perfect, formula sometimes get recalled for various reasons. We all know about the melamine found in the chinese brands, but all the major formula companies have had recalls for other reasons such as salmonella contamination, glass particles, and vitamin deficiencies, just to name a few.
~Many who start out mixing breastmilk and formula stop breastfeeding altogether early on because their supply drops.
If that's not enough to sway you, then I would encourage you to not start the formula until your baby is about 2 weeks old. There are two reasons for this. First, you know your baby will get nothing but colostrum the first few days, which is so important to the immune system. And second, if you are breastfeeding only, your milk will come in faster and you'll have a good supply.
EDIT: I see on your other question that you're going to be having your mom watch the baby sometimes. I imagine that's why you're saying you're going to feed both. Again, I'd suggest breastfeeding only and pumping breastmilk for when she's at your mom's.