This is a great series. It's the second I completed after my Jefferson collection. Like the OP, I was excited and on a bit of a buying spree. I bought three Buffs on
ebay, probably in 2012 or so, which was my first coin purchase online. I tried to get VG examples, no acid dates. I did get UNCs for the later dates, though. To me, there's no other coin that pops as much as an UNC Buffalo. To that end, I started a year set for UNC. I didn't complete that, though, as some years are really hard to find at 63-64, which is my range. I stopped hunting for an 18, 21 and 33 :). The complete set took me about 3 years. If I remember correctly, the 26 S proved the hardest. I recommend reviewing what fortcollins said, especially about weak strike and incremental steps that increase price considerably.