Which cube is the best for raising a potential to legendary?

I got a junk glove solely for this purpose. I don't even have 50mil so the SE neb is out of the question .

For future reference I'm using a reverse engnaw (or whatever the thief glove is called).

haha im in the same boat. Im currently using a DIPQ glove (i forgot to cube it during miracle time, i guess there is always the next one).