That's a difficult call to make. For a generic rune page, I would probably go fairly defensive, because it'll at least benefit every champ you play, even if it isn't ideal.
I haven't actually read much into current 'optimal' runes, so this advice may be a bit outdated, but...
Flat armor seals are usually pretty good, because a lot of early damage/harass comes from auto-attacks.
Scaling MR glyphs were considered the best for MR some time ago. Not sure if this is still the case, though. Theory there being that magic damage from spells tends to ramp up later on, so you don't necessarily need to stack flat MR early. Another good one for glyphs is mana regen, though that wouldn't benefit Shen at all.
For marks, something like flat AD would be generally applicable to a variety of champs. Could even do more flat armor there if you really wanted.
For quints... maybe flat armor or MR? I also really like the GP10 quints since I mostly play support, but extra income on any champ is never a bad thing.