Fletchling #66 Fletchling (1-Diamond, Common rarity) is the #66/71 card from the Secluded Springs set in Pokmon TCG Pocket
Once a formidable piece of disruption, Karn has largely fallen out of favor in more recent Eldrazi Ramp builds
Whenever five or more summons accrues, you can special summon it onto the field while tributing the entire board away, leaving the opponent with nothing more than a Token
While theres not going to be a set answer for every deck, Ive personally found that 4-5 is a good minimum for most decks I play in Commander, though if you play a deck that doesnt use a lot of creatures, you could easily find yourself playing more than 10
As a fine card on its own and one that's incredibly strong with other Humans on the battlefield, this is a great example of what you're looking to play in these kinds of decks