Arcades, the Strategist and Felothar the Steadfast are the two most popular, but you can also look to Doran, the Siege Tower, Doran, Besieged by Time, and Plagon, Lord of the Beach as some secondary choices
In the early game, you can apply pressure by attacking with multiple creatures and tokens and keep them protected from your opponents spells
[+1]: Look at the top four cards of your library
You draw X cards and the chosen creatures get +X/+X and gain trample until end of turn, where X is the difference between the chosen creatures' powers
Since Discord already lets mana of any type be spent to cast the copied spell, the main goal is keeping Discord alive and making the most of whatever random spell appears
How exactly could we do that