buy iron ore for 5 septim -> use transmute spell to convery to silver then gold -> then make 2 gold rings that sell for 60 each per gold bar(2 ore) 10 septim turns into 120 per 2 iron ore you can buy.

small things like that and the fact that any random gems while killing/mining are worth 10X more if you stick them inside a necklace or ring makes gold jewelery my biggest source of money.

but transmuting is boring as hell, you just stand there waiting for your mana to regenerate and hit a button once in a while....
hunting/flower picking is much more fun

I have fattened my coin purse by smithing jewelry.