Keep in mind, that Goho-M takes you to the entrance of the dungeon, so make sure you have plenty of those until you get a spell that takes you back. Once you go to entrance you can go and fuse your Persona cards you've gained. They'll be saved for later if you want to pull them out again. Make sure and Register them just in case though.
Keep in mind, before the deadline, there are generally a couple rainy days where you can't do much but try and reach the Meat Dimension. So it's okay to spend a couple days in each dungeon.