So I've been playing the Champ Pantheon for awhile now and all I know for runes that he needs is Armor Penetration. What other runes are good? Are yellow flat attack runes good or greater seal of might? Thanks!

All depends what role you are going to be playing. Here a good semi-glass cannon build. http://www.mobafire.com/league-of-legends/build/pantheon-phalanx-hoplite-51430

Just dont start out with a meki pendant first so you can throw more spears. Saw a Pantheon do that the other day and I raped him with garen .

A good set up for panth is armor pen on quints and marks. Hp per level on seals, and flat armor on glyphs. This gives you dominance and the 4-13 level range, which is when a majority of the farming goes on. control your lane to control both your farm and your opponent's farm.

I guess it would depend where you go as far as lanes are concerned. I have never played pantheon but from what I've seen I think mana regen/lvl would be decent on him.

Never get Mana runes on an AD carry. Only exception is maybe Ezreal. You want either damage or tank runes. Like Armor pen marks, Flat armor seals for early game. Makes no sense to get HP per level Seals and Armor Glyphs. Armor Glyphs are weak compared to the seals. If you want more health get Flat Health Quints. Since early game is when you are squishiest.