High level monsters RuneScape F2P

Level 1 - 20 Ranged: Cows in the Lumbridge Cowfield should be your target for these novice levels. An alternative switch is chickens, which are one of the best to level 15, but you would probably get bored after level 15. The cowhides sell for over 100gp each, and the bones provide fairly good prayer experience for your current level. Just bank at Beefy bill's every time you get a full inventory of cowhides. Another alternative to the cowhides are bringing them to Al Kharid's tanner and making hard leather. This is a longer more boring process, but very profitable and easy to obtain.

Level 21 - 40 Ranged: Begin fighting chaos druids. They drop a wide variety of very good herbs, up to torstol, which sells around 10-20k each. You won't be damaged too much if you aren't too low of a level, but if you are low-leveled, bring some food. Tuna is a good and cheap delicacy to bring. Dwarves are also an option, but only work well until level 30. And they do not drop as much of profitable items as Chaos Druids do.

Level 41-50 Ranged: Train on hill giants in the Edgeville Dungeon southwest of Varrock. You need a brass key, which is very easy to obtain. Just ask someone to get one for you in the dungeon if you do not own one. Hill giants drop limpwurt roots very often, sell for 1k gp a piece, and their big bones give good prayer exp. Or if you are not into leveling your prayer you can sell the bones for good gold. You can make a lot of money per trip. Another option is training on white knights until level 50, though they can work until 60, it is not recommended to train on them till level 60, because they do get boring and do not drop good items.

Level 51-60 Ranged: Train on ogres, located southeast of Castle Wars. They drop big bones every time and also drop good seeds occasionally. They are also a reliable charm dropper. As long as you avoid melee distance, you won't take too much damage. Though they don't hit that high, only around 6 or 7 damage.