A More Serious Look at Lulu
Lulu is a ranged support with unrivalled utility. Of course she can be found in other roles, we will focus on her support capabilities.
Pix Pix is an excellent source of early game harrass. Trying to get in as many auto attacks as possible can really cut down on the need to spam other abilities, saving your mana for more operrtune times.
Glitter Lance Provides a massive 80% slow (the same amount as Leona's ult) that can be used for pursuing or peeling as well as dealing decent damage.
Whimsy Probably her strongest ability. Using it on an ally can give them the speed to escape or to join the fight as well as an ability power steroid that overall makes it go well with AP assassins.
Using it on an enemy completely shuts them out of the fight and makes them very vulnerable. Used correctly on largest threat can almost decide the outcome of a fight.
Help Pix As a support this will be most useful as a shield, as it scales with resists.
Can almost eliminate the need for in fight pinks used for stealing assassins.
Can effectively double the range of your Q
Wild Growth Can be used for peeling or engages. Provides survivability as well as a huge AOE slow. Amazing with dive comps. Strong baiting tool.
Probably her best quality is her counter list. I will only list champions she does not counter or go even with.

She HARD counters all melee champions and can bully most anyone that does not have a massive range advantage.
Ex Build(of course you should build situationally as a support)
Lulu already has the ability to orchestrate fights this build does nicely at amplifying that ability as well as making you durable enough to stick around.