Hello PokeBeach!
My college friends invited me to play TCG with them, so I need some suggestions about what deck I should build. I saw in several places that the best option for beginners is a Double Starter Deck, but at the same time, I saw that they are not worth the investment. So... What do you guys suggest?
I suggest one of the Battle Arena Kits. These contain two decks like what you are looking for, but unlike most double starter decks (which I think you mean "Trainer Kits"), these Battle Arena Kits contain powerful cards that are used prominently in competitive play. Unfortunately there are only two Battle Arena Kits released, but I would recommend the Mewtwo-EX vs Darkrai-EX Kit if you can find it, as it is superior in both Pokemon and staple Trainers.