I find that silver is one of the best ways to raise crafting, after all you can steal it, and smith it at a very low smithing level. If you go to free worlds to buy, you can find that buying silver (ores or bars) is a lot cheaper on the official forums. (worlds - 200ea: forums - 400ea)
Tiaras arent that good to sell, but can be used to raise runecrafting...
Another good way to raise crafting is if you have nature runes. If you buy, say, 5k green dragonhides, you can make 5k nature runes, make green vambraces and alch for the same price you bought them for. (you may lose 20gp per hide if you buy them un-tanned)
From personal experience, soft and hard leathers are one of the worst ways to raise crafting when you are of a medium level. Simply because of all the work involved. If you can stick to crafting 50k coifs, then go ahead, but after that, you wont be able to sell them, and you'll have spent quite a bit on thread
OT: (wouldn't the *real* zezima be able to spell? lol.)