Sure you can transfer 2x drop or EXP cards to your other characters. Go into the Cash Shop and double-click them in your inventory, and they will go back into storage. Then you log in with your other character and take them out again. 
I enjoyed having my pet because it made looting easier most of the time. I'd recommend doing the Aqua Road quest (Kenta's Research, takes about 10 seconds if you've completed it before, maybe 20 minutes the first time) so your pet keeps up with you better.
I can't tell what class of character(s) you have, Cheez, but my strategy with my I/L was, right when I entered, drop to the ledge below me and Ice Strike the mushrooms, then drop down to each level and kill everything close to me. Don't waste time chasing 1 or 2 mushrooms that are out of range, just zap and move down. If a crystal drops and it's behind you, leave it for the next pass; get the ones that are easiest to pick up and move on, because they won't evaporate for a couple of minutes. When you get to the bottom, go back up both ropes but don't bother with the horny mushies at the top, because they don't drop crystals nearly as often as the zombie mushrooms. I only did them on the very first pass, or if the spawn below them seemed to be slowing down.
I never used more than 10% of my mana, but then I was 8x at the time so mana recovery was pretty fast.
Edit: Oh yes, and I did not use 2x drop but I did buy the extra tickets. I averaged 165 crystals per day, and I started a few days late, but on the last day I had enough to get the Moon & Star chair.
I enjoyed having my pet because it made looting easier most of the time. I'd recommend doing the Aqua Road quest (Kenta's Research, takes about 10 seconds if you've completed it before, maybe 20 minutes the first time) so your pet keeps up with you better.
I can't tell what class of character(s) you have, Cheez, but my strategy with my I/L was, right when I entered, drop to the ledge below me and Ice Strike the mushrooms, then drop down to each level and kill everything close to me. Don't waste time chasing 1 or 2 mushrooms that are out of range, just zap and move down. If a crystal drops and it's behind you, leave it for the next pass; get the ones that are easiest to pick up and move on, because they won't evaporate for a couple of minutes. When you get to the bottom, go back up both ropes but don't bother with the horny mushies at the top, because they don't drop crystals nearly as often as the zombie mushrooms. I only did them on the very first pass, or if the spawn below them seemed to be slowing down.
I never used more than 10% of my mana, but then I was 8x at the time so mana recovery was pretty fast.
Edit: Oh yes, and I did not use 2x drop but I did buy the extra tickets. I averaged 165 crystals per day, and I started a few days late, but on the last day I had enough to get the Moon & Star chair.