Level together or self leech later?

Hey yall, Im a returning player from the days when Gachapon tickets were still in the Cash Shop. I've been on for about a week or two and Im trying to find the best way to create an end game NL. I dont have the NX saved up at all so I have all the time in the world to fill so Im following a guide I found here on the forums, it's Akashsky's "Guide to efficiently leveling high base int chars with zero starting funding." Im following it because of my goals for the NL, filling the time, and creating both assisting characters and income.

Through multiclienting, the guide is telling me to make 2 characters and level them up together (I/L and Priest). Theyre both still at level 33 and Im too broke to afford buying leech (plus I want to do it in the most efficient manner so Im waiting till level 65ish before I start thinking about it). My main question here is, should I keep leveling both of them together or should I level whichever one would be a better leecher then self leech the other one?

If I do level only one first, which one should it be and at what level/point should I start leeching the other one?