The method that I'm using now is working pretty well. This is for lvl 19+ but can work for anyone doing Summoning, as the dungeon is home to many different types of monsters. Make sure to get all of your secondary items, spirit shards, and pouches into the bank before travelling to Brimhaven. Take with you about 1k, a hatchet, and food. Then pay the 875 gp to get into the huge dungeon. (If you think you're losing money, believe me, you're not. You'll eventually make the 875 for each trip back plus some more.) Go fight Greater Demons. They drop crimson charms quite often, and gold charms once in a while. Also, don't avoid the wild dogs. They can drop green charms and have given me quite a few. When you're ready to leave, DON'T TELEPORT OUT! Find your way out, then make your way to the cart service that takes you to Shilo Village. Once in Shilo, grab all the things you need for Summoning, including 20 gp. Use the cart service to get back to Brimhaven, and then walk west to the obelisk. Once done making your pouches, use the cart service to bank at Shilo, and again to get back to the Brimhaven dungeon. Repeat process, etc. etc. You get the idea.