What should your rune page look like if you are playing a support champion such as Janna?
I am an 1800 ranked support player. Originally I used to just run mana regen on my yellows, but ever since I bought gold per 10 yellows and quints, I've taken a liking to them.
The 5 gold per 10 gives you 1 ward every 2 minutes and 30 seconds, if you have 8 seals (yellows) of gold per 10s and quintessence gold per tens, it should give you 5 gold per 10. It also begins to apply this the second you get natural gold gain. So basically you start with 7 additional gold per 10 and a total of 20 gold per 10 seconds with Summoner Rift's passive gold gain of 13 gold per 10 seconds.
I put armor on marks (reds) for more resistance to absorb a bit of damage from harass/creeps attacking me if I decide to initiate, but you can go with magic pen too if you like to deal some extra damage. I exchange magic resist and mana regen on gylphs (blues) depending on the enemy/my champion (I tend to switch in the magic resist and armor runes for tankier supports like Alistar, taric, leona, and blitzcrank for engages against champions other than the bottom lane champions.
The goal of this Rune page: Wards, and lots of them, also you'll need the gold since you won't be taking any cs since your AD carry (a ranged champion with potential to deal lethal damage with the help of items through gold) will need it. It also gives you a faster philosopher stone.
Janna happens to be my main support, so my Janna rune page looks like this:
Marks (Red): 9 Armor Flats
Seal (Yellow): 8 g/10 1 mana/lvl
Glyphs (Blue): 9 mana/lvl
Quint: 3 g/10
Stats: 8.2 armor, 5 gold/10, 10 mana regen/5 at level 18
Additional gameplay tip: To make this most successful, do not stand in front to harass enemy champions. Stand behind your AD Carry and cast shield (Max shield first!) on them BEFORE they take damage or are about to deal damage to enemy champions. If it seems like you are going to engage, begin going ahead to cast your offensive abilities on the enemies. If an enemy ad carry is too close you can initiate by yourself with an offensive ability such as Janna's slow from W and your AD carry in most cases will follow through to deal damage.
As a support player, it varies depending on the enemy team as well as the support you are playing. A general page I run is flat armor reds, gold per 10 yellows, mana regen per level blues and gold per 10 quints. That page seems to work well with all supports. Specific supports can change out the yellows or quints for other things like MR, MS, health or health regen.