I don't have such bookkeepin but since I mostly buy + sell via Peakmonsters I can see my purchases there. The last 90 days I spent 23 $, I bought my first card there Sep 29th and in October + November spent most of my STEEM/SBD there instead of powering up. Right now I buy a booster pack each Friday - that's how I start my weekend ;) But buying booster packs is gambling - if you want to build your deck buy on the market.

I set myself a limit: I won't level my summoners beyond 4, perhaps 5. That lets me play well in Gold without having to spend enormous sums.