Indicated size is paper size, allow for a minimum 0.25" border of white space on each side
Once you exert the opposing character, you can then play a song with a cost equal or less than that characters cost for free
Other times its a strategy - for example, knowing you want to play as many lands as possible or win using an alternate win method, such as milling your opponent so that they lose when they cant draw any cards
One memorable collection I purchased a few years ago had a bunch of so-so rares from Invasion through Mirrodin
Daring Discovery Digsite Conservator Dragonologist Eclipsed Boggart Eclipsed Elf Eclipsed Flamekin Eclipsed Kithkin Eclipsed Merrow Etali's Favor Farsight Ritual Feral Encounter Follow the Lumarets Fomori Vault Freestrider Lookout Frontier Seeker Geological Appraiser Geometer's Arthropod Gilgamesh, Master-at-Arms Gishath, Sun's Avatar Guru Pathik Hidden Cataract Hidden Courtyard Hidden Necropolis Hidden Nursery Hidden Volcano Hide in Plain Sight Hit the Mother Lode House Cartographer Hurl into History Ignis Scientia Kaslem's Stonetree Living Phone Loot, Exuberant Explorer Lupinflower Village Marina Vendrell Master Piandao Michelangelo's Technique Mycoid Maze Nick Fury, Agent of S.H.I.E.L.D