Ranged - Crystal bow OSRS GP is not too bad, but it is not the perfect weapon for someone with your stats and cash. You should at the very least create a Royal Crossbow. I don't know how to do this since I don't have one, but I am told it's easy (and also the Royal Xbow is a tier 80 weapon). If you are like me and cba to make the crossbow you can always buy a Zaryte (60Mish), it's a tier 80 weapon, demands no ammo like the Crystal bow and also degrades very slowly. The grade 90 weapons would be the Ascension crossbows, both worth 255Mish every so to buy the two you'd have to spend 500M+.

Nex armours are good too, but they're definitely overkill for Slayer. I've Pernix and I do PvP and bossing with it only. I am really using it to camp ascension dungeon atm, but that's because I'm trying to get 99 Ranged this weekend and will need to get as much exp each hour as you can.

So that you've already got quite a lot of info from Aza, Fatia and Kamil, I would just add a couple of things: A participant with maxed stats like you ought to be seeking to get the POP (Player possessed interfaces, a brand new D & D) armours. These come in two types- a superior, non tradeable version, or a marginally weaker, tradeable edition. A significant difference is the tradeable version degrades to dust. However, these armour sets take an important quantity of time to obtain. Till then, I would suggest utilize the Bandos and Armadyl you've stored in the bank. There isn't much to gain from purchasing Nex sets when you'll be selling them directly after you purchase POP gear.

Please be aware that all weapons and armour are now organized TIER wise, by level. All weapons of the same Tier have the same DPS- a rune RS07 Gold scimitar is identical to some rune warhammer now.