Very fun champion to play that seems to work amazing if you have a friend you can talk to and organize... summer and I did an amazing Karma/Renekton combo. Here's my idea for a build:

9/0/21

9 Mark of Greater Insight
9 Greater Glyph of Focus
9 Seal of Replenishment
3 Quints of Fort

Flash/Ghost or Flash/Ignite (though i think flash/ghost is the way to go)

First point into the spirit bond for the chance to level 1 gank, after that you max shield and heaven wave... i really think it's entirely dependant on your opponents... if they're melee, i'd say shield, if they're ranged I'd say go for wave

Items:

Doran's Ring
Kage's Lucky Pick
Boots
Catalyst
Rod of Ages
Fiendish Codex
Ionian Boots
Deathfire Grasp
Zhonyas Hourglass
Rabadon's Deathcap
Banshee's Veil

Final items:

Ionian Boots
Rod of Ages
Zhonyas Hourglass
Deathfire Grasp
Rabadon's Deathcap
Banshee's Veil

The reasoning for the order of items is that with the ring + regen runes you have great early game spamming capabilities, the lucky pick early is just to maximize on the minimal gold output and have some quick AP, since she farms well this shouldn't slow you down too much. Next, ROA to give her some much needed health for the "in the thick of battle" support she'll be doing (also some tower diving), Codex for some CD reduc followed by boots and DG... those two can easily be swapped but the full CD reduc needs to be realized fairly early, hourglass for some amazing tactics, cap for the boost to ap, and BV for all around defense and to survive that first disable in battle.

The idea is to utilize her amazing offensive support abilities early on... spamming your lane to try and deny exp + an early gank item like DG makes her a very real threat. Pretty much, I see her at her worst in 1v1 situations... sure she's still fine, but she's definitely meant to have a partner in order to fully utilize her abilities. So by making her a legitimate threat early on, it forces the enemy to send multiple champs at you which forces team battles.

Now, I've only played a handful of games with her, but I also went for fast double rods and it worked extremely well. I think it's fair to say she'll be amazing in most situations as long you don't totally butcher the build... but for a basic foundational build, I think the one above should do very well. What is great is she is a support champ with a lot of punch which makes her excellent for ranked games... first pick AD carry, second pick AP carry, third pick jungler, 4th and 5th expected to go tank and support... now you can play a support champ that can actually take care of herself and you don't have to worry about the inevitable "stfu, you're 2/5" rage from the carry who failed to hold mid.

Plz, open for suggestions. Not sure if something like Rylai's would do well on her... I can't imagine it wouldn't... very possibly switch it for DG, I just like DG for it's CD reduc + dmg burst + slow... maybe even swap Rylais for ROA, though that is probably a bit too aggressive for ranked play