I dont think you really need cdr seals. cdr is quite easy to come by lately for both mages and marksmen.
and armor marks are not nearly as good as armor glyphs
for a mage champ its probly better to go with
magic pen marks
AP or MR glyphs
usually armor seals
and usually AP quints
may vary slightly but i would almost always get magic pen marks because the penetration helps boost your overall damage, especially if they dont have MR early on, it really shreds it up.
if on a diana, its possible to use atk speed marks as well instead if you plan on autoing a lot, like jungle for example to proc her passive more quickly.