Be sure to check the True Dungeon forums as well. Some people buy full runs so they can control the party difficulty level.
https://truedungeon.com/forum?view=topic&catid=736&id=257573
There are currently a couple of groups looking for more (LFM) for The Golden Obelisk dungeon (the intro dungeon). This dungeon will be perfect for people that have never played before. It is a little shorter (and therefore cheaper) and it is a sealed pack dungeon so you will be equipped just as well as all the other players.
There are also a couple of groups LFM for the Tomb of Tower Redux. This is a full 2 hour dungeon, but is also sealed pack format, so again good for new players. One caution - one group wants to run Tomb on Hardcore difficulty, which will probably be tough in sealed pack format. I recommend avoiding that one if another option also fits your schedule.
Good luck finding tickets.