You want 33 cards of the same factor and 7 other cards that block that same factor.
Try to fill a secondary utility with the 7 "block" cards: keeper removal, power bonus, damage bonus etc.
In your 33 mono factor cards you want to make sure you have 6 or 7 of each block color.
Stay away from high power cards (level 9 and up), you won't need them.
Distribute your cards over a bell curve of power levels, not too much high and low end... more in the middle.
Scale damage: Look for cards of these power level/damage ratios: 1-3, 2-4, 3-5, 4-6, 5-7, 6-8, 8-12 etc.
Play strategy: Just keep pounding away with your mono color, keep your other color(s) only to block with unless you are certain your opponent does not have that factor in their deck then use them for their secondary utility. Do not block cards doing less than 4 damage to you ever, unless they are keepers or have other undesirable effects (chaining more cards etc)!
I believe you will get a quite decent win ration with this deck against randoms.