I really relate to what you said about the ordinariness of playing cards being a kind of cover. My first ‘serious’ readings were with a battered travel deck in hostel common rooms, and no one batted an eye because it just looked like I was killing time. One of my most accurate readings was a three-card spread for a friend debating a job move: 8 of Diamonds (work and steady effort), 7 of Spades (mental burnout), and 3 of Hearts (new emotional connections). It laid out the exact arc of leaving a draining role for a more cooperative team a few months later.
Over time, this deck started developing its own language with me.
The 4 of Clubs consistently shows up right before I take an unplanned trip or change my routine, so I treat it as a ‘shake up your schedule’ card. Your mention of sevens being ‘epitome cards’ lines up with my experience, too. My 7 of Hearts almost always flags relationship illusions I don’t want to see, which feels sharper than the tarot 7 of Cups. Using that same deck for years has really proved your point about the cards holding onto our readings - every crease on mine has a story behind it.