What Seals do you recommend getting? I don't see many of them being good if I were to get 9 of one set.
For Marks I think I'll go for 'Hybrid Penetration', at 9 Marks, that's an extra 8% Armor Pen. and 6% Magic Pen.
With my Mastery for Offensive characters, that'd mean I'm ignoring 10% of their armor and MGR. Not much but every little bit counts.
EDIT: Reading up on Seals via LoL wikia (at work atm), I might go for Attack Speed, 9 of those gives me an extra 6%ish Attack Speed, with my Glyphs & Mastery, that means I start with 20% attack speed, meaning my ADCs would be close to 1 hit per second start of the match.
I might also get the mana and health Seals for another Rune page focused on Mana dependant characters.