U will need to do this :
At least 44 runecrafting and at least summoning 57.
Stuff u need:
Spirit Ghraak summoning puch
Pure essence
Nature talisman / tiara
Few Ring Of Duelings ( 8 )
What u gonna do is :
Tele to Castle Wars bank .
Then right click on Spirit Ghraak and press interace and teleport.
And walk to nature altar . Tip:when your summoning points are low u find obelisk next to altar!
When u have crafted all essences then tele back to Castle Wars !