One last thing to remember: Use abilities as often as OSRS GP you can. When I cast Fire Surge on an glacor, and utilize a magic power I do not make use of the arrows in any way. Similar to arrows 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 everything you need to know concerning the EOC in your head. Perhaps I'll create a guide about this. And if you need any further assistance, you can contact me hereor on the your game "Renegaderp".
If you're not able to purchase an official crossbow, you should have thought about purchasing the Armadyl crossbow. Always utilize 2H or dual weaponry to slay tasks. Choose the most powerful weapon you've got. If you have a lv 80 ranged wep and the lvl 80 melee weapons as your highest tier weapons choose the weapon that the monster is weakest (according to the triangle of combat).
You will never need anything other than bandos or barrows to slay tasks. If you do need any lvl 80 weapons I would suggest to go for chaotic weapons, and spend your money on other items. I would recommend that players choose the lv 90 stuff if they've got cash to burn. But it's your choice.
In terms of bolts, you can now use any bolt on any bow. The compatibility aspect has been eliminated. If you use level 80 royal bolts in conjunction with crossingbows with LV 70, the bolts will come with a damage cap , as if they were the level 70 bolts. If you own a level 60offhand bow and the mainhand bow, the mainhand bow is capped at old school runescape gold 70 bolt damage while the offhand bow is capped at the level 60 damage. It's true, I buy Royals because they are cheapest and it's not really a big deal regardless.