Most efficient ROA

I have heard that using a dab rig is one of the more efficient methods, however I do not want to invest in a rig just for dmt and I no longer smoke pot.

My question is, which ROA is more efficient between e-cig or an oil burner? What method uses the least amount of spice for a breakthrough? I have a nice box mod capable of temperature control and variable wattage well above what is needed. I am asking because I want the spice that I have to last as long as possible. Mostly interested in breakthrough experiences more so than lower dose trips.