Don't have much time so I won't give you a large block of text. I play Lulu quite a lot and I see nothing good in your build accept maybe some of your auras. This may sound counter-productive but look at some of the other Lulu builds.

I play that mana hungry early. yes. simply cause I do harass consistently. I play an aggressive early game but that is my play style yet I have played lulu so much that I am almost never caught off guard where I have no helpful skills available. This is the only character I use that much mana with early game though and it works VERY well. I also aim to lane as long as possible. I take Clarity not only to help myself but others and in the late stages of a team fight, It can help your entire team by making their skills available.
This build is weak on mag resist with its core. I aim for a better late game which is not abnormal with an item dependent build. You normally do not have to get much more than that late game unless the enemy team is focused on ap damage(which the scaling runes help with).
Keep in mind this build ALLOWS you to spam your skills but is not necessary.
Clarity helps your team more than you think and people will love you just for bringing it (as long as you learn to watch your allies' mana bars). If you do not wish to bring clarity, don't. There is a reason I mentioned optional spells.
As far as ionian boots go, as a tank there is no reason you should not want to be focused for damage...that is the purpose of the role, and you want to be able to use your abilities as often as possible, but not without sacrificing tankability. If you need to run Glitterlance can slow an entire team and Whimsy can increases your movement speed.
This build Consistently nets me about 7-8 wins out of 10 games because in a way you are able to carry the carries by allowing them to take much less damage(giving them the ability to build for more damage).
I will never add anything to this build untested as there is no point in an untested build, and I do suggest optional items/spells in the guide to cater to what you might expect to be up against. Most of which were mentioned in the above posts actually.
Thank you for your feedback and while your suggestions are noted, most of them have been tested with this lulu build.
As with any guide, play smart and build the character as you need it to be built.

If I read this build I'm like "Why play this style" in the first place xD
Ok, I haven't played Lulu as a tanky too much, or actually never :p

But anywayz, this build feels weird.

• Your opening is awkward, who so many mana potions, how about spamming your spells less?
  Also, just one ward? As far as I know you need 2 at least if you want to get Philosopher's Stone at your first recall. (I haven't taken the gp/10 runes into account, don't really know the numbers there.
• Clarity has only one goal in the game, show that a player does not know how to use his/her mana.
• Your item build for the late game is also weird, you sell your Ionian Boots of Lucidity? You might as well place a sign above your head "Target me I can't run away".
• Why Locket of the Iron Solari over Randuin's Omen when playing tanky?
• Why Aleisa's Miracle, just take Mercury Threads for the Tenacity.

A tanky build would be a bit more like this (I think, not tested, order might and will most likely be wrong)

• Mercury Threads (alternative: Ninja Tabi, Mobility Boots)
• Frozen Heart, stats: mana, cdr, armour and a neat taking aura.
• Shurelia's Reverie, stats: cdr, mana reg, health reg, neat aura
• Randuin's Omen, stats: armour, health, sustain, neat aura and active

Total:
- Quite some armour
- Mana should be fine (though I know quite some Lulu players spam a lot of skills.)
- Cooldown Reduction: 40% (46% with masteries)
- Tenacity: 35
- Aura: Finish with some damage/utility items such as Abyssal Mask, Zhonya's Hourglass, Rylai's Crystal Scepter, Will of the Ancients or Warmog's Armor.

Summoner Spells:
- Flash / Ghost, up to personal preference.
- Teleport (solotop, not sure if this guide is meant to play there)
- Exhaust (bot-support) / Clairvoyance, up to personal preference

-1 because of Clarity, which should never be seen on a support EVER, but also:

- You shouldn't use Greater Seal of Gold, double gold/10 seals are for very passive supports, which Lulu isn't.

- I'm really not sure about double scaling MR runes. Are you aiming for a strong early game or late game?

- 5 mana potions? Are you THAT mana hungry?