Early in the game i find starting with Faerie charm and pots a lot better than Dorans' ring and a pot because you don't always need the damage early, this just helps you lane for longer.
I only do my first back when i have enough to buy Sorcerers shoes so i can come back and have that penetration to keep them at bay. If i'm doing well at that point i buy Chalice.

Once I get my boots, i rush athenes as soon as possible, even if that means stealing some jungle mobs or ganking other lanes for a sure kill. Because by this point you should be needing to put down the damage, but leblanc is mana hungry. so this helps you go all Yandere on your enemies for longer, once i get athenes i dont go back unless i need health or i can afford needlessly large rod. Your next item NEEEEEEEEEDS to be Deathfire because this will give you alot more burst to get all dat Monay!!

Rylais as your fourth item... WHAAAAT?

Yes. Rylais as your fourth item is actually a really good idea. it gives you some nice damage and health, also the passive helps you lock up your enemies with your E and helps you stay on the pesky teemos who run away.
But for your fifth item, you can either get Rabadons if you want to stop faster or you can get Zhonyas if there are quite a-few team fights. I generally get Zhonyas instead of rabadons because you dont know if the enemy can get you down first, so this acts as insurance.
But now i beat you're questioning "WHY THE HELL IS THERE A WARMOGS", yeah i did at first when i experimented. This gives you a whopping 1000hp and 1% HP regen every 5 seconds. which goes really well with Athenes if you wanna just run round for ever. But that health also helps for insurance. Leblanc is quite a squishy champ and this helps with team fights so it takes longer to burst you down. You can opt to get this then zhonyas (or rabadons) so you can postpone that 3260 or 3300 gold, for pots and what not, now you have your 6 items.
Maybe you're not tanky enough or not enough damage. This is the point you decide to get the Rape hat or the really old mans rod by selling athenes, (hehe), Rabadons will help you destroy your enemies while you have good hp or it can be a downfall, If you think you need more hp and your damage is fine. get a Rod of Ages. this just whams up your hp and gives good ap so you can run around going "AHAHAHAH IM ***********ING LEBLANC, SUCK MY 3200 HP AND 550 AP, AHAHAHHA"