I was going to ask more specific questions but I think a general discussion thread would work best.

What are some good ways to use disposable gold to improve the levelling speed/experience?

Off the top of my head:

Engineering bombs for DPS/threat management
Mana/health potions for improved sustainability/ bigger pulls
Buff foods (?)

But I haven't put any of this into practice and I haven't looked at any specifics. Any thoughts?