An excellent set-up for slayer which is fairly cheap is to put on a Slayer Helm, or Neitznot (sp?) Helm until you acquire the slayer helm Amulet of RS gold Glory, Fighter Torso (can easily be acquired within a few hours) Platelegs of Torag's or Verac's Plateskirt , if you'll use prayer for your quests as it offers prayer bonus, Whip /Dragon Scimitar Dragon Defender, and Dragon Boots and Obsidian Cape (unless you already have the skillcape or firecape).
Keep in mind that this is just an advice for equipment and you are able to switch things to a different level. For instance, you could replace your defender with an Obsidian shield when you believe you require the extra defensive boost, and you can always make use of dragon platelegs if you do not want to fix the armor on your barrow, as it breaks down in combat.
Additionally, if you do not meet the requirements of the quest for the helms, GET THEM. If you plan to do any sort of killing, take on this Smoking Kills quest buy OSRS GP as soon as you can. Don't be afraid of trying various things and discover which ones work for you.