User blog comment:SharkMoon6621/Smithing!!!/@comment-3152761-20130321222826

By far the most plentiful ingots are Dwarven Metal Ingots, as long as you have the carry weight and the time to clear even one Dwemer Ruin. Iron items makes you virtually no experience but if you don't mind a massively tedious process, then I'd suggest that. Lexicon quest helps a ton too.