Some as examples, in addition to the ones mentioned above: Pidgey line, Poliwag line, Machop line, Dratini line, Abra line, Krabby line, Koffing line, etc
Of course, the most straightforward way to get gems is by purchasing them with real money

0.3%inclusion 9 decks 3.27K decks Happy Hogan, Dauntless Driver 21%inclusion 4 decks 19 decks Invisible Woman 0.3%inclusion 2 decks 586 decks The Scarlet Witch 0.1%inclusion 2 decks 1.36K decks Hawkeye, Master Marksman 1.0%inclusion 1 decks 98 decks Top Commanders Kolodin, Triumph Caster 47%inclusion 1.80K decks 3.80K decks Balthier and Fran 55%inclusion 1.31K decks 2.39K decks Depala, Pilot Exemplar 61%inclusion 988 decks 1.61K decks Edward Kenway 6.2%inclusion 806 decks 13.1K decks Setzer, Wandering Gambler 30%inclusion 514 decks 1.72K decks Captain Rex Nebula 33%inclusion 458 decks 1.39K decks Samut, the Driving Force 9.0%inclusion 423 decks 4.71K decks Kykar, Wind's Fury 1.7%inclusion 232 decks 13.7K decks Breya, Etherium Shaper 0.8%inclusion 180 decks 21.6K decks Pia Nalaar, Chief Mechanic 12%inclusion 152 decks 1.22K decks Optimus Prime, Hero 2.5%inclusion 118 decks 4.69K decks Astor, Bearer of Blades 8.8%inclusion 95 decks 1.08K decks RMS Titanic 8.1%inclusion 90 decks 1.11K decks Dr

Exalted is great with Commanders you seek to kill with Commander Damage, which isn't that uncommon in Jund
This is a pretty steep rate in 60-card formats, and limits your ability to spam cheap artifacts and execute combos