Gleaming Overseer
any more than that you risk getting color-screwed
An innersleeve, outersleeve and toploader are the bare minimum, but you may also want to invest in some even more secure Screwdown Holder that will completely protect it from the elements
As long as it says legendary creature under the art, or if its a planeswalker that states it can be played as a commander, they can be your leader
I evaluate ban list cards based on how they would perform if they were legal in Commander
If we think of each block as either new territory or a revisit, we have: Mirrodin [Revisit of Antiquities], Kamigawa [New], Ravnica [Revisit of Invasion] Time Spiral [Revisit of Everything], Lorwyn [New], Shadowmoor [New] Shards of Alara [New], Zendikar [New], Scars of Mirrodin [Revisit of Mirrodin] Innistrad [New], Return to Ravnica [Revisit of Ravnica], Theros [New] Khans of Tarkir [New], Battle for Zendikar [Revisit of Zendikar], Shadows over Innistrad [Revisit of Innistrad] Revisit-New-Revisit-Revisit-New-New-New-New Revisit-New-Revisit-New-New Revisit-Revisit Time for more New then