While using the Divination skill in Runescape, what should I be turning my memories into to get maximum time to exp efficiency? Should I turn them straight into exp, or should I cycle between energy and enhanced exp.
Turning memories into energy gives the smallest amount of xp. Turning memories in xp gives medium xp and turning both energy and memories into xp gives the largest chunk of xp.
If we look at a random wisp type (e.g. here), we see that for example Sparkling wisps give 5 xp per memory if converted to energy, and 15 with enhanced xp. This means that alternating energy and enhanced will give you 20 xp per 2 memories, while just using normal turn-in gives you 2 * 12 = 24 xp.
If you do not care about the energy, then turn your memories into as much xp as you can by turning in both energy and memories. Otherwise only turn memories into xp while keeping the energy. If you are very rich, buy up energy from the grand exchange and turn all your memories into as much xp as you can.
However, keep in mind that energy is used in crafting various things. They are both used in Invention, as well as various trinkets in Divination itself.