There certainly are more experienced members than me, who probably will contribute here (I'm a fairly recent newcomer as well, been using Kaleidescape for less than a year). I haven't really set out to create a strategy, but I've reflected a bit on what I actually end up doing.
A few factors to consider:
- effort spent cataloging/importing/buying
- amount of money spent on movies in total (throughout your life as a Kaleidescape owner)
- amount of money spent over a shorter period of time
- quality of movies bought (SD-HD-UHD-HDR, Atmos)
- willingness to buy movies multiple times
- time taken to build your movie library
- desire to exploit special deals and super bundles
- desire to immediately have complete sets of movies.
I prioritize low cost, don't mind spending time and effort to build my library (I'm in no rush), but would like the highest quality available. As I dislike buying the same movie twice unless the upgrade price is low (say $5), I try to only buy 4K HDR/UHD at $9.99 or less. (Try, not necessarily succeed). I typically don't buy the movies I've got D2Ds for unless I want to see them, both to make my movie budget last longer and to see if the movies show up cheaper in a bundle. I get a surprising amount of pleasure from looking through special pricing deals, operating with a fairly fixed monthly budget and trying to guess if it's better to buy or to wait (the same movie can end up in different special pricing offers). Kinda odd, but what can you do
As for TV series I get the impression that having them on sale is a fairly recent development (those with longer history here can probably confirm or deny). There are a lot series not in the store. The pricing per season can be a little high I think, so again I hold off until there's a sale. Older series can be low quality SD, so it's a question of whether you should wait for HD or not. (Parks and Recreation got an upgrade to HD fairly soon after it was on sale, for instance). I usually end up buying a few seasons from series on sale, just to see if they catch my interest. Then again, if they do then they are no longer on sale, leaving me with the dilemma of waiting (forever?) for them to go on sale again or buy the remaining seasons full price. Haven't quite nailed this part down yet ...
If I wanted to quickly boost my library with movies through D2D offers, I would probably still focus on getting 4K HDR/UHD and buy those going from DVD quality to 4K priced at $8.59, and from HD to 4K priced at $4.92. I would skip going from DVD to HD at $4.50, due to the possibility of having to buy again if they suddenly became available in 4K.