Not an expert but may be able to help.
First, speech is a stealth skill & covered by the Thief Stone - one of the 3 (I think) stones that can easily be found when heading to Riverwood from Helgen. Utilizing that stone makes you learn stealth skills 20% faster.
Second, I always rest an hour in a bed I own before I sell anything. The "well rested" bonus adds another 10% to the speed of skill increases (all including crafting, combat skills, sneak) for an 8 hour period. If my character doesn't own a bed, I wait until she does. After my nap, I then give a coin to the town beggar because that has a temporary boost to your speech/persuasion. If you're worried about the one gold, if only because it was yours or like the challenge - you can then steal it back. Not that I would ever do such a horrible thing
.
Don't forget about skillbooks & even more importantly trainers. If you're worried about the cost, which may be a normal reaction to new (and even stingy characters such as myself) - you can work on pickpocket at the same time and take the money back - if that's the direction your character is going.
And it's already been said that the value of transaction inputs the increase amount too. So, I always improve things before I sell them. You can make a potion of fortify barter with monarch butterfly wing, dragon tongue & tundra cotton. You can also use hagraven claw but those are too rare when more abundant ingredients do the same thing. I didn't use them forever because I figured "what good is 30 seconds when it takes me longer than that to go through this crap to find what I'm selling?" - but then I realized the clock stops after the barter menu comes up.
Making stuff makes your crafting skill increase faster than improving & uses more material. I usually just improve what I loot, which boosts craft skill & adds to their worth which benefits the value during transactions. Again, I tend to collect a bunch of stuff - then improve 30-40 plus items at once. And again, if your trying to level up then I would sleep for an hour in a bed you own. I never try to level up crafting or speech without napping.
As for waterbreathing, I lucked out on this character & pickpocketed one very early in the game off the Jarl of Whiterun
. Don't know if your character is a thief but I got a lot of my early enchantments that way & I think sneak was one of 'em.
Hope this helps.
