Chess.com Lessons
Well there are several thousand lessons so chances are that even with the best of intentions, you're not going to go though all of them.
That said, if you are serious about improving, they are a fantastic resource. The gold and platinum levels are kind of a joke though, you need diamond to make any headway. Some of the very earliest lessons are kind of a mixed bag in that they don't really give adequate feedback for wrong answers, but the newer stuff is excellent at pointing out where your thought process is flawed. There is a core group of lessons that give a wonderful introduction to the game and beyond that are in depth instruction on every aspect of the game. Gm Wolff's tactical motif series will absolutely change the way you view chess, but some of the lessons need to be repeated a few times before the fabled "pattern recognition" kicks in, but tactics probably give you the most bang for your buck. I'm 75 so admittedly doing the lessons hasn't made a major difference in my rating, but at least I'm getting worse more slowly...
And yeah, I have done quite a few.
Lessons
Thanks so much for your response! I'm 28 and I don't really have much in-depth knowledge of chess. I think I may start a membership and go ahead and start running through lessons and hopefully improve my game!