This might have been asked already but here it goes anyway.

I know buying and selling stuff increases speach craft. If I wanted to buy 50 iron ingots, would i get more exp buying 1 at a time or does it mater?

K-Ray

I have heard it both ways. I saw in a youtube video on how to level speechcraft/alchemy (buy/sell ingredients/potions) that it was the total amount bought/sold. Though I read on these forums a couple times that it is by each transaction as it was in oblivion. I am curious as well on this.

Levelling is much more intricate than Oblivion's system. Different weapons level up the same skill at a different pace. Not all Alchemy potions give the same amount of skill increases (this is very simple to notice). Not all spells give the same experience when casting them than others (Muffle gives a LOT more experience for Illusion than casting Clairvoyance does). So I wouldn't be suprised at all that selling a lot of identical items in many transactions does not give more "experience" than simply selling it all in one go.

It should be easy enough to figure this out by starting a new character on the PC and adding items to sell. But having the Construction Kit would help even more.

Passing speech checks (Persuasion, Intimidate, etc) gives quite a bit of experience though, but it's fairly limited in how often you can do that (if you don't abuse a current glitch).

From what I've heard and what I've seen in game it's the total worth of a single item, so if you sold 50 potions worth 1000g you'd get exp for one, individually you'll get 50x that amount, but a potion worth 10g would give little exp. I've sold groups of items in a single lot and haven't raised a level but selling the same group individually I'd get one half way though selling. So yeah sell individually in most cases unless the item isn't worth much then you may as well sell in a group you won't get much exp either way. It's not set to one sale equals one exp but one sale worth more exp the higher the items base cost, I'm not entirely sure if whether the amount your getting for it count's, like if you had an amulet on zenithar and the blessing of zenithar, you'd earn more exp for the 20% extra your getting. It would make sense to, but then again so would selling a bulk of items at market being worth more skill then a single.
I'm not sure about buying though or even if it gives exp, I've never gained a level buying items.

Hmm...

So it is raised by the amount of transactions and the amount raised is governed by the value of the items in that are being bought/sold?

I will get more experience selling a potion worth 500septims than a potion worth 10 septims. Since it is still the amount of transactions done it is best to sell off each item individually yes?