If you aren't able to get an official crossbow from Alexis's blog

One last thing to remember: Use abilities as frequently as you are able to. Should I be casting Fire Surge on OSRS gold an glacor and employ a magic skill I do not make use of to make use of any arrows. The same applies to arrows that are within the range. For slayer tasks, you'd want to avoid ultimates, and focus on basics and thresholds, until you can use Guthix' Blessing to heal, or Berserk/Metamorphosis for some crazy damage.

Then I've explained virtually all you need to know regarding the EOC to you. Perhaps I'll write the guide to this. And if you need any further assistance, you can contact me hereor via the games like "Renegaderp".

If you aren't able to get an official crossbow, you should have considered getting an Armadyl crossbow. Always go with dual weaponry to slay tasks. Make sure you use the highest level weapon that you have. If you have a level 80 ranged weapon and an lvl 80 melee weapon as your top tier weapons pick the weapon you are weakest against (according to the triangle of combat).

You'll never need anything other than bandos/ barrows for slayer tasks. If you need Lvl 80 weapons, I think its better to buy OSRS GP get chaotic weapons and save your cash on other items. I would recommend that players look at the lv90 stuff if they've got cash to burn. But it's your choice.