I'm a little insecure about buy runes. Runes costs a lot of IP, so I'm researching a bit before.
I know that I need to be in level 20 to buy the best/final runes.
1) I need buying only "Greater" runes. Am I correct?
2) How do I know if a rune is "primary"?
3) By example, let's say that I want to buy Cooldown Reduction (CDR) runes. I found out that I will need Focus and/or Celerity runes. Celerity has Glyphs and Quintessences. Focus has Glyphs, Quintessences, Marks and Seals. It's implies I can (If I want) fill an entire rune page with CDR Runes? What an efficient buy of CDR Runes, considering that I want buy Magic Penetration and Mana Regen Runes too?
4) I've got the runes list here, but it presents ALL runes, so is really boring to check that list. There is some list/table where we can check only "primary" and "greater" runes?