From 22 to 31 make Granite Crab pouches. This is quite efficient, as well as costing tiny charms. You will need 1,300ish blank poucheswith gold charms, iron ore and some 10,000 spirit shards. This will probably cost you in RS Gold the mid, to high 200k. Between 31 and 40 you'll be able to make Vampire Bats. They are a decent source of exp and their supplies aren't as hard to find than others....