You need 30 gp Runescape money to get started. Go to Port Sarim, west of Draynor village, and ask one of the people in the blue uniforms to go to Karamja and pay them 30 RS gold. When you get there, walk off the dock and you should see a house. Enter the house and talk to a man named Luthas. He will ask you to pick bananas. Answer "Yes", pick bananas, put them in the crate, then talk to Luthas to collect your moderately earned 30 GP. If you would like more RS money in multiples of 30, ask him to get another 30 GP for doing the job again. Stay here for a long time and repeat this job for several times if you need to spend several thousand on items.

Get to Port Sarim and do the banana thing. Put a bottle of rum in the crate then go in and collect your Runescape gold. Then go back outside and to Port Sarim get a white apron and go get a job in the grocery store at Sarim. Search the crate in the back and take the rum and some bananas. Then go to the bar in Sarim, give the drunk the rum and then, when you are done, go up to Varrock or someplace and sell the bananas to make enough RuneScape gold.