First, I don’t recommend doing this unless you have atleast 60+ combat and adamant armour and above, with a rune weapon. In your inventory bring 30gp, nature runes (if you have 55 magic), a lobster pot (if you have 40 fishing) and the rest filled with lobsters (or any other food that heals 10+.) Now head down to Port Sarim and pay the guy to go to Karamja. Once on the island go past the bana plantation and make your way through the forest to the volcanoe, climb down the rope into the volcano. In the volcano you will notice skeletons and spiders, walk past the spiders and you will find the lesser demons, killing lesser demons is great money, pick up all the mith and above drops aswell as fire runes and you will make tons of money. When you run out of food go back to the banana plantation and fish some lobster and go back to the volcano.
The next monster that we will be hunting is hill giants, most people can kill these considering they are only 28 combat. For hill giants you probably not need food unless you are under level 40, but bring a few pieces of food, to be safe if you are 50 or below, you will also need a brass key. To get to these you will need to walk west, out of varrok until you get to the river, follow the river north until you come across a small building, enter the building and go down the ladder. In this very large room there will be hill giants, kill them and pick up the money, big bones, nature rune, law runes, and limpwurt roots.
The next, and last monster I shall be talking about is a very close cousin to the Hill Giant is the Moss Giant. For these giants I would recommend being 40+ combat. If you are below lvl 60 bring food, but besides that you don’t need much. To get to the giants folo the road north from Varrok east bank until you reach varrok sewers, enter the sewers and keep going until you reach a spider web continue through the spider web and then make a right and go down a small path and you will be able to see the Moss Giants! When killing these pick up themoney, bigbones, and runes.
When killing monsters just remember to have fun with it and to pay attention considering that some of these monster are quite strong. Happy hunting!