I have a nice amount of IP and I might buy some champions, though I want to make sure I have all the runes.
For marks I have 9 Flat AD, 9 Flat AS, and 9 Flat MP.
For seals I have 9 Flat armor and 9 scaling health.
For glyphs I have 9 flat cdr, 9 flat mr, 9 scaling MR, and 9 scaling AP.
For Quints I have 3 flat cdr, 3 flat AD, 3 flat MS, and 3 flat AP.
4ManVotedAgainst1 votesDepends on if you plan to main a particular champion or set of champions. Tailor them according to what is best-suited to what you are likely to use.
VikingRaid1 votesDepends on if you plan to main a particular champion or set of champions. Tailor them according to what is best-suited to what you are likely to use.
Any examples?
4ManVotedAgainst1 votesAny examples?
Sure, 
has a passive that adds more Attack-Damage the higher his Armour, and you would likely obtain Armour-Quints for him IF you use him a lot. 
has a passive that adds more Ability-Power the higher his Magic-Resist, and you would likely obtain more Magic-Resist-Related Runes for him, except you will find that he's very mana-intensive, and will likely combine it with Mana-Regeneration (although with enough experience you learn not to spam his E in order to avoid always going OOM very quickly).
You will need to tell me which specific champions you use a lot or plan to use a lot for me to give more specific examples. For the sake of helping to give you a head-start against a lot of your competition, I would recommend that you start maining 
, for he can do any role that isn't ADC, and is a strong pick, and the Runes I would recommend that you don't already have are entirely Attack-Speed for both Marks & Quintessences. Use them for (Attack-Speed should be at 29% if both Marks & Quints are full of Attack-Speed).
also plays similarly to . has less counters than which is one of the reasons I would recommend you really learn & get your skills polished as .