Best skill to lamp?

I followed the advice of lamping herblore since account creation but now my herblore is lvl89. I don't know how high herblore I need, I am still in the mid game/ early late game (70-90s melees and 90s range/mage), so my only exposure to pvm at this point has been simpler bosses which I use regular super melee or ranging pot for. I don't get the hype around divine pots. I have not raided. I don't know what high level pots people actually want to use.

Other skills I'm curious about lamping are slayer and prayer. I've completed all hard diaries and am working towards elites now, and that means lots of chunky exp lamps. I'm 75 prayer and 81 slayer. Getting slayer up a little will let me kill more profitable creatures, but I can see myself easily going past 99 slayer going for boss drops. Prayer on the other hand, I don't know how to effectively pump it up besides getting it up super slow passively through slayer and bossing. At the rate my herblore has gone up, I see it getting to 99 naturally, as I do frequent farm runs and do my farming contracts.