That really depends on what runes you have available, who you like to play, and your general play style. I tend to play pretty defensively early since I prefer champions who are stronger late game, so my runes tend to reflect that. Some general recommendations from me:
- General AP Page: AP Quints, Armor Seals, MR Glyphs, Hybrid Pen Marks [General defenses and damage boost]
- AP vs AD: AP Quints, Armor Seals, Scaling CDR Glyphs, Hybrid Pen Marks [Lets you buy an early Tear of the Goddess and Seeker's Armguard without losing out on CDR]
- AP vs AP: AP Quints, Scaling Health Seals, MR Glyphs, Hybrid Pen Marks
- Tank Jungle: MS Quints, Armor Seals, Scaling MR or CDR Glyphs, Attack Speed or Hybrid Pen Marks
- Passive Sustain: Health Regen Quints, Armor Seals, MR Glyphs, Attack Damage or Hybrid Pen Marks
- Autoattacker: Attack Speed Quints, Armor Seals, MR Glyphs, Attack Damage Marks
- AD Assassin: AD Quints, Armor Seals, MR Glyphs, Armor Pen Marks
- VS Strong AD Early: Armor Quints, Armor Seals, Scaling MR Glyphs, Attack Damage or Hybrid Pen Marks [Nice against champions like Riven]
- VS Strong AP Early: MR Quints, Armor or Health Seals, MR Glyphs, Attack Damage or Hybrid Pen Marks [Nice against champions like Rumble, Leblanc]
- Tank Support: Health Regen or Armor Quints, Armor Seals, MR Glyphs, Armor Marks
I'm pretty happy about my current rune set up, so feel free to look if you're curious.