Way back in March I made some quick change pants from Anna Maria Horner's book Handmade Beginnings. The 3 month size, shown below, still fits Isaac (although barely).
He also has a pair of 6 month quick change pants which have fit him perfectly now. I need to make some more sizes for 9+ months.
The pants are super easy and super quick to make - they took me about 2 hours each. I really like the fact that they're reversible, no exposed seam allowances anywhere (therefore no need to serge!), and you can adjust the cuffs as your kiddo grows. As an added bonus, not much fabric is needed for them so I was able to pull from my stash instead of buying new. I have at least 4 more fabric combos set aside for various sizes of pants. Just have to find time to actually cut + sew.