It's perfectly possible to grow up in this game and discover everything yourself. You progress gradually from overland questing to public dungeons to more advanced content. Trying different sets, builds, classes is a major part of the fun and has kept me going for a long time.
What's different is, if you're perhaps coming from another MMO or for whatever reason you want to jump straight into group content / guilds and progress quickly up the ladder. This isn't the greatest thing, if you ever intend to return to questing. The better you get, the more frightfully boring and meaningless you may subsequently find questing, because the combat is so easy.
Thus, unless your goal is strictly endgame, taking a build from an endgame player - this includes Alcast and probably every single YouTuber - is honestly not great. These are people who often work with a minimum of sustain, be it due to their playstyle or the group compositions they run in. Their builds will be effective for what they do, but that doesn't necessarily make them the most fun. They will be OP for overland content, while they may paradoxically be too squishy or lacking in sustain in the hands of a new player. If you are competitive and you simply want to reach the highest levels of endgame as quickly as possible, while not becoming stuck in some blind alley and developing bad habits, then fair enough. Learn all you can and go with someone else's build. The upside is that you'll probably learn about group-oriented skills in the process, especially if you are a tank or healer, and your guild will thank you for it. However, if you are more of a solo player or you're still in the questing phase of the game, there is no need for any of that.