A card's value depends on a few things
Sacrificing your own creatures is, as already underlined, a big point in the deck, seven creatures target it
Once you get the hang of the game, you probably wont need it as much, but when youre still learning, it helps you to know where to place your cards
Reverse holos do the opposite by making the frame and background shimmer while keeping the creature flat
Clarabelle Light on Her Hooves 211/204 Clarabelles price point is something of a surprise to me as I havent seen a ton of chatter about her being a particularly strong card
Some of these are just very good early game cards that allow you to fix your draws, while others have very splashy effects like giving you extra turns or allowing you to steal some of your opponents cards