If you are new to poker, the CC 30 day course under "
poker strategy" will give you a good allround foundation for competing in micro or low stakes tournaments. If you want to progress further into medium and high stakes games, this is the time, where paid training sites like Upswing Poker have their biggest merit.
Early on it can almost be a disadvantage to learn to advanced GTO strategies, because these are usually not the most effective against the mix of fish and bad regs, you are actually going to encounter in your games. So my advice is to learn the basics of the game first and a more traditional exploitative style like the one, Collin and Katie teach in their course.