By getting experience in it? Hm... leather is always a good choice. Right now, you can make leather gloves. Kill the cows outside Lumbridge, bank in the castle, and repeat. Once you've got a fair amount of hides banked (250+), go to Al Kharid and start tanning them. Afterwards, craft them into gloves, boots, cowls, vambraces... whatever is the highest item you can make. That should shoot it up. Later on, you can start mining and/or buying silver and making tiaras. Seems to be a popular method, but rather boring... Hope that helped!