For levels 1- 15 Edit
Agility iops show go to dare devil crabs until lvl 6 or 7, it's up to you. Then once you've reached divine sword you should go to chafers to get more exp and really easy to level with divine.
levels 16- 20 Edit
Just train and train at chafers unless you are P2P then join a kaniger's hunt you will level really fast.
Every fight is worth about 10k exp up until you are a really high level. The higher you level and wisdom the more exp you get.
F2P's should think about going to Astrub and train on Crackrocks or other monsters, ( Crackrocks do drain ap away so it isnt good if you need the ap)
P2P's should go to blops and biblops. Weaker to you element.
F2P's should train on crackrock's or keep on doing the field dungeon.
P2P's should train at gobb dungeon with a group or solo with a lvl 39 chance sacrier, as they can heal hard.
Also You should start to get a Prespic set for higher wisdom. (Note F2P's can wear them aswell.)