Hi, and welcome to the board.
I too am wet behind the ears, so I can't offer much advise. However, I recently put a 1/2lb. of heartfelt beads in my coolerdor. They seem to be more than adequate for my humidor size, and are super easy to use. Also, they are holding right around ~65% humidity. I couldn't be happier with these beads. What percentage of relative humidity are your beads? I think that extra large tube will be more than sufficient for your new humidor.