Once I'd finished my raw ASM runs I thought I'd go for a CGC run of 9.4 White Pages for issues 100 to 200. It was a way of continuing collecting ASM I suppose, but my heart wasn't fully in it as I'm not actually a big slab fan. 101, 121, 122 and 129 were quite pricey then so I decided to go for quantity first and picked off the cheapies thinking I'd pick off the big guns as and when bargains appeared. They didn't of course, and prices increased hugely in a short period. So I made the wrong choice on reflection from a price point of view. My 129 ended up costing me £700, almost double what I could have got it for had I purchased it first.
So my advice, based on my own experience would be to get the pricey keys first, on the basis that they may increase in cost far quicker than the non keys which in theory will always be freely available.