FYI, Kaladesh packs are on sale for 100 gold from today until April 17th. Time to cash in those saved up coins!
Figures, it would go on sale literally the day I finished up the KAL set. Any chance the other sets will go on sale too, or should I save up coins until Amonket drops? Right now I have 100% KAL & AER, and 60% ORI.
Based on the past sales history, the second most recent set(s) typically go(es) on sale a couple of weeks before the new set drops ( i.e. Kaladesh is on sale before Amonket drops, SOI & EMN were on sale before Aether Revolt dropped, etc.), so AER is likely to be the next sale in 3-4 months.
So, Amonket will be a good buy or most likely SOI & EMN. Origins has gone on sale somewhat randomly in between, and BFZ & OGW haven't been on sale since Kaladesh dropped, so they could be back on sale soon-ish.
Therefore (can you tell I'm a lawyer? Sorry btw...I do real estate!!!), I would either invest in SOI and/or EMN or wait for Amonket. Origins may also be a safe bet to complete since it has been on sale more recently than BFZ & OGW.
/end over-analysis of possible random occurrences