What would be the ideal setup if I wanted to Pk and/or do GWD/Bossing with Ranging? Like my equipment, inventory etc. Tips would also be appreciated.

Pk i would sya knives/void and c bow!

I don't PK anymore, but I can help with the bossing setups.

Range isn't very convenient for every boss.
The main bosses people prefer to range at would be Nex, Armadyl, Corporeal Beast, Saradomin.

The gear obviously will be about the same for each of these, as you are ranging.
Nex being the boss that would generally have the highest requirements to do.

Ideally for ranging bosses, you'd want the best gear to do it.

Nex: A very high-level boss requiring 2-10+ people to kill depending on gear/levels. Overloads are generally required for every team you go with. Full Armadyl or Pernix, or Armadyl with Pernix piece is the gear that's most commonly seen. Void is also used with a deflector + Armadyl OR Pernix Body. A Pack Yak is highly advised as you want to be able to get multiple kills per trip. Inventory would consist of claws + brews / Restores / Antipoison and Ruby Bolts. Chaotic Crossbow + Eagle Eye Kiteshield / Divine / Elysian are recommended.

Armadyl: A Godwars boss that is commonly killed by rangers. Armadyl being the armour most widely used here. Karil's is possible to use here, but not ideal for the situation. Again, Overloads are ideal, but you can get away with having Extreme Range here. Depending on team size, overloads aren't always needed. Unicorn Stallion familiar is advised, or even a Pack Yak (although not necessary). Inventory would consist of brews/restores (with Overloads). OR if you're in a bigger team, you don't need brews at all really. Surviving on a Unicorn + Enhanced Excalibur is very easy.

Saradomin: Also possible to be ranged while running around the room. I am not familiar with this boss/method, and therefore, will not go into much detail about it.

Corporeal Beast: A ranger is usually common in bigger teams, as people like to have someone specific to 'stun' the core. Ruby bolts along with the best range armour you are willing to bring would be ideal.

With all of these setups, the best gear will obviously make the kills faster and the trip more profitable. Chaotic Crossbow + Rigour being the two main Dungeoneering rewards that help with Range. Very advised to get if you're planning on ranging a lot.

As I stated before, I do not PK anymore, so I don't have any comment on the best gear for that.

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Karils, a Chaotic Crossbow, Ranger Boots, and an amulet of fury will do fine for any ranging situation you are in.

Welfareish setup for pking would be:

Black dhide body, rune pl8 legs, archer helm, glory, snakeskin boots, rfd gloves, ava accum, msb/rune c bow. Spec wep would be either AGS/Korasi/Rune c bow with d bolts.

Invent: ranging pot, 3 ppots/super restores, v tab, veng runes, spec wep, rocktails, 1 brew and 1 super retsore for that brew.