Standard mana bases are already very good and the mix of enemy and ally lands are currently balanced, so my guess would be ally lands in Magic Origins to go along with the enemy fetches in Battle for Zendikar
The front of the card tends to be more important than the back, especially regarding centering, but both should be measured carefully
You dont even need other chocobos, since Choco, Seeker of Paradise just draws you a card whenever you attack with it, but additional birds really make it that much better
Green tends to have the biggest creatures at any point in the curve, so it lends itself well to stompy strategies that make use of 2-mana 3/3s like Werewolf Pack Leader and Keen-Eyed Curator and such to outsize your opponents and rush them down
Looks like Wizards has once again found a way back into my wallet, and I can't wait to see what the full lists come Monday.
It is incredible how a few extra wrinkles drawn onto a character can really sell that feeling of 'I am in absolute agony.' Seeing a character so well-known and recognizable distorted in this way makes for a very uncomfortable image