I'd definatley get 40 attack for f2p pking but if your member try getting magic up, do Desert Treasure and get 50 attack and try G-Maul rushing, if it doesn't work out, move on and get 60 attack for d claws or d scim to dds, very good combos , or get 70 attack for whip or Sara sword and combo ss to dds or whip to dds or whip to claws, your preference, now the last option is 75 attack for an AGS no BGS no ZGS but all the way AGS. Hope this helped
from past experiences i learn'd that 60attack seriously kills if not 75 for ags or even not more if you got 80 for chaotic pure with that is just pure rape face
If i was you, i'd stick at 20 attack, for that awesome VLS k0, or get 50 attack for Gmaul. That would also level up your CB level leaving you open to getting better loot. Let's face it, who wants a pair of black Dhide chaps and a coif after koing a shitty ranger?