This is the most basic way to get free cards, and it will remain a staple of the game for the foreseeable future
Psyduck is by far the most wanted Illustration Rare followed by N's Zekrom, Rocket's Mimikyu, and Cynthia's Spiritomb
Speaking of common promos, in the most recent Banned and Restricted Announcement, they snuck in this little gem

Primal Genesis Commander (1) Planeswalker (1) Creatures (28) Angel of Sanctions Atla Palani, Nest Tender Cliffside Rescuer Desolation Twin Doomed Artisan Dragonmaster Outcast Emmara Tandris Feldon of the Third Path Flamerush Rider Garruk's Packleader Giant Adephage Heart-Piercer Manticore Marisi, Breaker of the Coil Ohran Frostfang Rampaging Baloths Roc Egg Sakura-Tribe Elder Scaretiller Selesnya Eulogist Soul of Zendikar Tahngarth, First Mate Tectonic Hellion Thragtusk Trostani, Selesnya's Voice Vitu-Ghazi Guildmage Voice of Many Wayfaring Temple Wingmate Roc Instants (10) Beast Within Druid's Deliverance Fresh Meat Momentous Fall Naya Charm Rootborn Defenses Second Harvest Slice in Twain Sundering Growth Trostani's Judgment Sorceries (10) Cultivate Explore Farseek Full Flowering Ghired's Belligerence Harmonize Hate Mirage Hour of Reckoning Phyrexian Rebirth Shamanic Revelation Enchantments (6) Colossal Majesty Commander's Insignia Elemental Bond Growing Ranks Intangible Virtue Song of the Worldsoul Artifacts (5) Idol of Oblivion Lightning Greaves Mimic Vat Sol Ring Soul Foundry Lands (39) Ash Barrens Blossoming Sands Boros Garrison Cinder Glade Command Tower Evolving Wilds Exotic Orchard Gargoyle Castle Graypelt Refuge Gruul Turf Jungle Shrine Kazandu Refuge Krosan Verge Myriad Landscape Naya Panorama Rogue's Passage Rugged Highlands Selesnya Sanctuary Sungrass Prairie Terramorphic Expanse Forest x8 Mountain x4 Plains x7 The Commanders This Naya deck has populate as its main theme

Team Up has been a consistent seller this year, and its price has only continued to rise
These English cards have three gold stars in their respective bottom-left corners as their rarity symbol in the same position that the Japanese cards have UR placed