If your deck is on the slow side, choosing to draw (go second) rather than play (go first) can be reasonable to give you that extra card
Howling Mine, Dictate of Kruphix and Kami of the Crescent Moon all fill this role, but The Immortal Sun does it without giving your opponents and advantage if you'd rather avoid the group hug
Midrange strategies can play Lumra as a potent six mana threat that incidentally provides them with plenty more lands to help fuel their one-for-one trades and slowly accrued advantages, creating a situation where creature lands might be the only real win condition they need if Lumra gets answered
The most successful card resellers have a clear brand that allows them to build a loyal target audience
Return to Ravnica had focused on five of Ravnica's guilds (the Azorius Senate, the Golgari Swarm, the Izzet League, the Cult of Rakdos, and the Selesnya Conclave) while Gatecrash dealt with the other five (the Boros Legion, House Dimir, the Simic Combine, the Gruul Clans, and the Orzhov Syndicate)
DMU gives you the chance to pull borderless prints, though
