This is going to depend on your play style. If you are going to try to get as much exp an hour as possible and play for the maximum efficiency of an hour, you should skip Fire Giants. However, this is a boring play style in my opinion. Personally, I do not mind doing them at all. If you want to kill them fast and easy, go to a multi combat area with a cannon, and it will take less than an hour to solve your contract. If you want to do them chill and easy, just get your prayer armor from the bank, put on your protection from melee, and AFK them. No matter how you try and kill them, they are going to be pretty decent exp. At the higher combat levels you can easily get 100k an hour exp here. The drops however are really bad. You won't make a lot of money killing these, so do not go here thinking you will get rich.