In the furnace, you'll receive molten glass for RS gold the glassblowing process. Through the use of a glassblowing pipeline and a glassblowing pipe, you'll be able to create Unpowered Orbs. To make the process simpler, finish the Hand in the Sand quest. This will let NPC Bert give you the equivalent of 84 buckets of sand each day.
Another option for leveling at this point is achieved by purchasing gold ore by Blast Furnace and smelting them into the bars needed to make Gold Bracelets. These will provide you with huge amounts of Crafting experience , and they can be later dissolved with High Alchemy for a small profit and additional Magic experience.
If you are the Ultimate Ironman, your options are a bit less. The best bet in this case is to go to Port Phasmatys and bulk buy soda ash and buckets of sand. Then, go to the furnace close to the port and melt them into molten glass used to make glass items. Always aim for the highest of a level item. You can upgrade the level of your cheap OSRS GP skills to gain the number of experiences you gain. After making your item, sell them to a general retailer and then switch worlds to replenish your supply.