Well I think you should always train with OSRS gold slayer, it shouldn't take too long to receive 70 whatsoever; maybe a couple of days depending on the length of time you perform every day. A great set up for slayer that's fairly cheap is to use - Slayer Helm or even Neitznot (sp?)
Bear in mind that is simply a proposal for equipment, you can always switch things up. By way of instance, you can swap out your defender to get an Obsidian shield should you really feel like you want the additional defensive boost, and you may always use dragon plateleg's if you do not want to be fixing your barrow's armor because it degrades in combat.
Furthermore, if you don't have the pursuit requirements for your helms, then DO THEM. If you plan to do some slaying whatsoever you should do the Smoking Kills quest as soon as possible. Don't be afraid to try out different things Buy old school runescape gold and see what works for you.