Pro:

Very fast at jungle clear.
A lot of utility during team fights.
Can stop ultis like Nunu's during a counter gank with a simple Whimsy.
It is a damn Yordle.

Cons:

She can be squishy if running into enemy jungler.
Ganks become usefull and viable starting lvl 6, early game ganks require a good poke from the lane.

Lulu's kit is a very good one to stop lane champs from running away during a gank. The best combo you can do to get a perfect gank is put your shield on your ally champ. Give him the speedboost with Whimsy and then cast Glitterlance from their place to slow the enemy and stop him from running away, once you reached lvl 6 this can even be prolongued by using your ulti first to knock em up. This does require a fast hand.

An other advance you have during draft games is the confusion you'll make when you pick Lulu as a first. They'll try to counter her on top lane, mid lane or support on which you can counterpick, and then blow them off with Smite in the loading screen.

I started playing Lulu when she was free and fell in love during the first game. I started out as a support, but I wanted to do more with my passive. So I started googling and found a full AD Lulu build for the top lane and wanted to try this. This worked versus tanks, and melee champs but the moment they have range, you are screwed so you lose your farm and start to fall behind. So off to google again and found a Lulu jungle build. I thought this was a troll, and the items weren't all that good teamed up in my opinion, but I mixed my own experiences with the build I'd found, and mixed my Lulu top masteries with the build I found. I had some trial-and-error on my first game which we lost too close to be true because 1 enemy champ got fed and started to knock out our other lanes. I tried again and succeeded in the way I planned Lulu to work. That is why I made this build, to give ya'll my way of playing the cutest yordle in League of Legends.