1-10: At these levels, you will simply make leather items.
10-54: Spin Flax into bowstrings. This method doesn’t make much xp per hour (still more than the previous items created), but you will make some nice profit at this level. Normally, the flax is half the price of the bowstring. As you see, there will be some profit for you (about some 100ks). I recommend you to use the spinning wheel in the Lumbridge castle at the 1st floor (at the 2nd floor, there is a bank).
It is quite easy to do and you can also do something besides this, while you are training for 99 crafting, like learning!
I have been asked how many of them you need to do. You will have to make about 869k bowstrings and nearly 80M profit (this was calculated on the 5th of November 2012).
at level 29: An alternative is to make hard leather shields. You also make profit and faster xp. But I heard they don't sell well... it's up to you! (You also can buy the stuff you need and you still make profit - recommendable if you can get rid of "junk")
54-66: Buy powered orbs and their respective unrobed battle staff and make complete battle staves. You can even make some profit out of it depending what the Grand Exchange prices are and street prices and this can even be around 300k per hour. Don’t forget that you are only allowed to be 100 pieces of both items all 4 hours. I advise you to buy them in an early stage of your training (already at level 1), so you will not have to wait eternities until you have enough orbs and unorbed battle staves.
66-80: You will make sapphire bracelets. They require a cut sapphire gem (saves time and money) an amulet mould and a gold bar. The best furnace to use is the one in Edgeville, wearing the Varrock armor. This makes some loss, but it is not so much, but you make good xp per hour.
80-99: From now on, you will be making green dragon hide body. I strongly recommend you to use the stealing creation needles, because the double the xp you make per green dragon hide body! Using sc needles will cost about 55-60m. This will be the item to go for 99 crafting. Of course, it is not forbidden to make a higher level dragon hide, but they will increase the loss drastically.