Lulu is one of my favorite champions now, and I build her full support/babysit. She's awesome and mischievous. Her ulti knocks up and heals for a lot, making her an invaluable support.

Depending on what team you have and what team you're going against, your items will differ. For more damaging teams, you want penetration. Glitterlance is a great nuke, so you can build a bit of AP for damage with it. You always want health and armor and magic resist, as any support/tank.

Always be around your team, and in team fights either ulti yourself or the LOWEST HEALTH teammate. Whimsy the most damaging enemy, or the enemy that should be focused (whimsy will help you get to team fights or to help a low health teammate escape). Help Pix! is a burst damage (shield to your allies), so be sure to use that to help out teammates, as well. She has great CC and can do a good bit of damage throughout the whole game. She is very harrasy early game, so take advantage of that. Farm/kills won't be much of an issue, as the items I've shown are cheap and if you're good support, you'll get plenty of assists and gold. She's so fun to play and fairly easy to learn.

She's an alright jungler, but as you're trying to play support, don't always be in the jungle.

She has great support abilities, but they cost a good bit of mana, so if you feel like you're always running out, you can buy mana regen. I also would NOT suggest going straight AP, as that build is expensive and her abilities don't really match with the typical AP champion. Only Glitterlance is really affected by AP.

Lulu's unique abilities and support makes her a literal game changer. Expect to not get many kills but many assists. She is OP as of now as a support.