We used 204 size 1-2 diapers, a gentle step between size 1 and size 2. Size 1-2 diapers are between size 1 and size 2 diapers, and are rated for 8-18 pounds. The folded height on a Pampers Swaddlers diaper size 1-2 is half an inch shorter than the size 2, but otherwise the same. We used them when he was 12 and 13 pounds, using the last one the day before he turned 3 months old.
Overall, in diapers, we've had the best luck with Huggies and with Pampers. The most effective diapers are soft, so that they curve into baby shape easily. My favorite diaper is the Pampers Swaddler because it's soft, because the stretch waist helps hold it on despite lack of booty, and finally because they support Sesame Street (I like Disney, but Sesame Street rates higher, possibly because I grew up on it).
Since size 2 diapers also run up to 18 pounds and we probably won't see that until around 32 weeks, I can buy size 2 diapers in bulk now. (It's risky in the smaller sizes. I met a 20-week-old baby already in size 3 diapers, and his mom had to exchange size 1 diapers from her shower for size 2 in the first month!) Then again, I've been happier when he's not at the high end of the weight range for his diapers, so I might step up by 16 pounds which should be around 26 weeks of age. Or, if he keeps nursing at this rate, assuming I hold together, maybe next week. He seems quite intent on growing right now at 15 weeks!