Multi pking: 100 combat is basically a must if you aren't a maxed pure. We have a guide on the discord for setups etc. Having high magic(around 82 is what we recommend for ice blitz) and Desert Treasure is recomended.
Singles Pking: Literally every combat level. Although it helps to have a special account for singles pking (if you aren't maxed).
Questing always comes first.
Don't be that pure pker that has to wear a combat bracelet and risks 5x more in their gloves slot. Don't be that berserker pure that doesn't have barrows gloves, or that doesn't have vengeance.
1 defence (all of these should be using mithril gloves from Recipe for Disaster):
Defence pures: these accounts should always have vengeance.
For most accounts you also want to do:
Dwarf cannon quest. Just in case you decide to get low hp.
one small favour. For guthix's rest (highly advised when fighting people with 75 attack).
If that didn't cover everything, look up some guides on the account build you want.