Here are the general rules of thumb I follow when addressing this question myself: If my deck has green, the best mono green mana ramp spells are usually better than my multicolor options
Since the buyer still wont have most of the sets cards at that point, for the most part it wont really matter which cards the buyer receives from the booster pack
I guess Wizards of the Coast finally printed an exciting wall by making it an eight mana 0/30 creature that grants all your other permanents indestructible
2-star trainer cards (like a full art Brock card) do not have any flair options for it
The starting point of pretty much every Commander deck I build is setting aside slots for 38 lands, 10 ramp, 6 spot removal, 3 board wipes, 10 card advantage (mostly card draw), 2 recursion, 1 graveyard removal, 2 flexible tutors