Well, actually, you can find a trader in mournhold, but if you do enough quests in eat empir hall Bloodmoon storyline, thr will be a Trader with 10,000 gold too, in Solsteim. NOTE you must have game of year edition so you can go to the trader in mournhold and you can get out, then go to sostheim lotta gold person.
A 3:
If your talking about cretures,Id suggest creeper in cadera
A 4:
There's a talking mudcrab merchant south of a Daedric ruin called Zaintinaris, think thats the spelling, anyway, he will buy weapons, armor, and potions only but he has 10,000 septims every 24 hours plus you can just rest right in front of him so you can sell alot of stuff quicker. Someone mentioned the Creeper but he only has 5,000 septims per 24 hours. I havent used the other merchants mentioned so far. The mudcrab is the best bet for someone early in the game. Just do a google image search and you will come up with a map to help you find him. Hope this is helpful.