Sold off a shitload of stuff, but kept some of my dupes for now; ones that are bound to get new/awoken ults in the future or are HOPEFULLY getting buffs at some time or another (looking at you, wizards and ninjas (though I did sell my dupe Hanzo and my dupe riders (including both dino riders because I've had that mf'er since the start and i've never used him in almost two years of play))).
Kept:
one of my dupe Leilans
two of my three Ame no Uzume
my wizards even though I still think they're boatanchors unless they actually get farmable skillups and ults
my dupe Norse (Thor and Freyja dupes)
my dupe Skuld (she's tempting to sell, but she could get a sweet ult too, so idk)
my dragon swordsmen
dupe Orochi
all my collab silvers
my fruit dragons except for the dupe lemon I pulled at godfest
my dupe Kushi
my dupe Astaroth (though I sold my Amon and FA Luci dupe because there's no way I'll ever use Amon since I have no drive to skill him up, and even though I went to all that effort to skillmax my first Luci, I have still never used him)
my dupe Ras (I guess having multiples is a good farming thing if I ever have the drive to make three Awoken Ra)
both of my Apocalypses (he got gud)
Arcline (don't really have a use for Arcline since I have Sun Quan, but maybe someday)
my fairytale girls (pls get ults)
my dupe Persephone (torn on making two of her healer ult, idk yet)
The above is all on the chopping block but they're all in limbo. So for now, I wait.
And no, MP shop is definitely not just for ultra-whales, it's just who it favors most. I've done my share of IAP, but to consider me a whale would be to say that I was but one of the tiniest whales in the sea, relatively speaking. And I still can put this to good use. Non-IAP can benefit too, it's just that they have to wait longer, as Chirei said.