Old as the world's largest food festival and RuneScape gold money-making activity is not the most cost-effective method of earning gold-plated pieces in OSRS but it's also the most relaxing, without a doubt. For non-membership users, the only option is to fishing for lobsters at Musa Point near Port Sarim that can bring in around 20k gold every hour.
It's not the most cost-effective deal however, if you've joined and are looking for ways to increase your angling skills Catching infernal eels will yield approximately 280k gold/hour while being almost AFK. It's not even necessary to use feathers lures. If you're not scared of PKers and are looking for something a tad more intensive dark crabs are to be found, earning 380k gold every hour.
For those who prefer to stay in the comforts of cities, this method is a good fit for most. It doesn't require a membership account, has minimal entry requirements (just up your craft skills to 6 and you're ready to go) It also helps you master crafting, and generates about 100k gold pieces per hour simply by grabbing several gold bars and necklace molds before putting them in the furnace. Considering that's non-membership method and taking into account that the requirements are essentially nonexistent it should be your option if you're looking to make gold in a hurry.
Mining runite requirements are straightforward even though they are high. You have to raise your Mining up to 85 levels and buy a dragon pickaxe or runic and a looting bucket. Once you're set you can head for Lava Maze in the Wilderness to find where Wilderness Mines are located. Be aware that it's Wilderness, and PKers are prevalent, so don't bring valuable things that you would not want to lose, j melee weapon, and food with you.
With that, you are completely prepared to mine runite rocks. They spawn two per world, meaning it is necessary to buy runescape 3 gold world move around a bit.