Most of these are opinionated; picking between 2 or 3. I usually like running what I think best, If it runs smoothly with the deck, If it's needed. Does it need to be there to make the deck actually run? Or is it a card I'll occasionally need? Does it make the deck? Or does it just support the deck? My best idea is to look at a skeleton of the deck look up the decks name I.e. : Burning Abyss, and base your deck off that skeleton
Tweeking a deck takes time, the best way to tweek a deck is through actually testing the deck. Toss cards you dont need and add ones that you want to see more often.
There are cards that are considered staples in decks such as Vanity, a deck may have staples from it archetype E.x.Triple Cir, Scarm, and Graff in a Burning Abyss deck, You always run 3 of those. So when building a deck keep in mind staples and such.
That's all from me
~KndyMn