Bear in mind that's RuneScape gold only a suggestion for gear, you always have the option to switch things up. For instance, you may swap out of your guardian for an Obsidian shield should you really feel like you need the extra defensive increase, and you may always use dragon plateleg's if you don't want to be fixing your barrow's armor because it degrades in battle.
Also, if you do not have the quest requirements for your helms, then DO THEM. If you plan to do any slaying whatsoever you should perform the Smoking Kills quest after possible. Do not be afraid to try different things and find out what works for you.
This whole installation will cost you approximately 2-2.5M, also is an excellent overall installation for slaying. Don't forget to also use a number of that cash to purchase super sets (Super Strength/Attack/Defence potions) that you should use on ALL your slayer tasks. It may look like you are spending a good deal at first but it speeds your tasks up noticeably and is well worth it, and you will be profiting from your Old school runescape gold slayer drops / hint scrolls anyway.