Some are mechanically twisted, like the one that instructs another player to tap someone's father, or the one Charlie 'MoistCr1TiKaL' White plays that lets him make a copy of any card he can think of, but many are just funny, juvenile gags
Several factors influence Journey Together card values: card condition (mint cards worth 3-5x more), rarity (holographic and rare cards command higher prices), first edition status, PSA/BGS grading scores, and market demand for specific Pokemon
It has great synergy with creatures and counters, so Id expect it to do some crazy things
Trainer cards take up most of a Pokemon TCG deck, since they can help the player in many ways, such as taking a specific card from the deck, drawing more cards, healing a Pokemon, and even disrupting the opponents strategy
That is not always going to work, because your deck is not always going to run the way you want it to (unless you are good at shuffling your deck)