Best way to obtain marquee characters

What is the best way to spend crystals to 7-star a newly released marquee character?

They will often have packs of related toons that are all required for a single event.

Until one of those toons hits 7*, your best spending is on those packs. Once one or sometimes two characters hit 7*, however, then some of every pack is going to shard shop currency and it becomes more economical to purchase shards for the individual characters that have yet to reach 7*.

Now... THAT SAID ... they often skew the odds so that you are more likely to get the earliest characters released in those packs. As a result, for maximum crystal efficiency, you probably need to hold off buying any shards of the first toon or two that are released. Wait until all of them are released and then look for the "faction" pack (not really a faction, but "group" or whatever -- you know what I mean).

Then buy the heck out of them until one hits 7* and hope you get lucky with the rarer toons.