This is a build meant for people playing Lulu mostly as a support and who are short on money. I have found that with this work up I never have any issue completing my build and often can go back at the end of the game to switch out some lower quality items for for AP or HP as it is needed. That being said I am aware there are better items out there, I made this cheap cheap cheap and in a way that still gets the job done.

Pros: I feel that this is one of the best balanced champs between being able to support other and still harass the other team.

Cons: You won't be healing your team through a fight, and you won't be killing champs on your own often, very middle of the road champ.

As you can see my Quint and Seal are devoted to gold, you may find this unnecessary but again it offers some great gold and allows you to let your carry get the minion kills.
My Mark and Glyph are simply to offer some more spell pen. and AP even though you are a support and with this build you will likely not be killing champs on your own end game I do think that it's always good to be able to dish some dmg when needed. You also get plenty of health and mana regen through items.

I built 10/0/20 to get the cool down and magic pen from the office tree along with a little AP and then the rest into the utility tree for the gold, and other obvious reasons that you can see for yourself. Note I did not take the points for the extra 40 starting gold because I feel that with my build it is a waste. By lvl 6 or 7 I am usually up to upgrading my boots so I do not feel that the extra 40g is worth the 2 points.

I start out with the Regrowth Pen. for the health regen that it offers early game. This always me to stay in lane for a long time and really just go back when I have a bunch of gold weighing me down.
My first trip back usually gets my the Philosophers Stone and base boots.
Second trip back is then the Heart of Gold, and Kage's Lucky Pick. At this point you should be getting 35.25 gold over 10 or over 3.5 gold a second.
I then delay getting rid of my extra gold by upgrading boots and getting a Haunting Guise. I go with the sorcerer's boots because my cool down reduction will already be maxed out, and the Haunting Guise is just a great all around early to mid game item, it is cheap and covers a lot of bases.
I then upgrade my 3 gold items into the items you see above and in that order.
Then late game I add some more AP and spell pen to help in late game team fights.

Glitterlance: I start with this first because it is a great way to keep enemy champs off of the minion kills, and the slow on it is great to help with ganking.
Whimsy: I put one point into this early for the movement speed to help get back to the tower faster and also to help chase down champs with greater movement speed. I also do not often turn enemy champs into fluffy animals, I just use that to interrupt their ult's. I do not use this for the increased ability power, I just see that as a bonus when it does happen.
Help, Pix!: This is the second spell that I get up so that I can both use it to shield an ally champ and also it is a great combination with glitterlance for a quick nuke combination.
Wild Growth: This is just a great spell. Cast this on your tank when he jumps in for a team fight to make him large and in charge, it can also be used as an emergency heal to avoid giving up a kill to the enemy team.

Note: opening up with a glitterlance, followed by a help pix, and then use the fact that pix is following them to get an extra glitterlance off while they are running away.

I personally go with Flash and Ignite. The Flash helps with chasing down an enemy champ or more commonly getting out of an enemy's ult. Ignite is just always a great spell, especially early game for those early kills.

Note: This is why I have a point in the offence tree for this spell. Get a bump in AP and attack dmg when Ignite is on cool down.

I'm not going to say that any summoner spells are "bad" on lulu, I think that it really comes down to how you play your champs for what spells you need.

In summary I put this build together for those less gold endowed then others. It offers a pretty good all around build between support and being able to get kills in game. Constructive criticism always welcome.