The first season is quite straightforward in its approach: recruiting a dysfunctional group of individuals with unique skill sets and abilities to stop an immortal villain through time travel. Admittedly, I was mostly in this for Sara Lance because she is my absolute favorite character of the Arrowverse, but I warmed up to a lot of the other characters as well. Throughout the season there is a level of development that happens with quite a handful of them. Sara, unlike on Arrow, is a main character and is treated as such since we do get some development of her struggling with the aftermath of having been recently resurrected, and also her dealing with the level of self-hatred from everything she is and has done, this also includes balancing the bloodlust. She is also given more humor and playful snark, which goes into the vibe of the show being lighthearted and fun, which I personally love. Leonard Snart and Mick have intriguing character developments on the show, as well. They're basically criminals who initially seem to only care about themselves than the rest of the team, but as the season progresses their characters shift and change from what they experience. Mick certainly surprised me the most, and I love that while he turned around and his motivations and perspective changed, his personality more or less remained intact, but still shows how much he has grown as a person due to what he experienced while held by the Time Masters. Leonard sacrificing himself in the end for the greater good (giving the big "fuck you" to the Time Masters) and thus becoming a hero was heartbreaking, but also heartwarming.
Another character I ended up loving a lot is Rip Hunter, who is also deeply flawed but incredibly human. His personal vendetta sometimes gets in the way of the safety of his team, which does cause tensions at several points, and rightfully so, especially when you consider that he wasn't quite forthright from the beginning when recruiting them of his true motivations of stopping Vandal Savage in the first place. He is rightfully called out and even punched several times for placing them all at risk or keeping important information from the rest of them team, and he acknowledges these faults due to his own selfishness. By the end of the season, particularly with learning the truth about the Time Masters and their plan of manipulating him (and the team) since the beginning, he truly tries to not place anyone else in danger for his mistakes, which is something I really love seeing in characters, both acknowledging their flaws and attempting to change. Another thing I loved is his interactions with the rest of the team, particularly his dynamic with Sara since I believe Rip considers her an equal. It's fascinating to watch.
(It also doesn't help that I find Arthur Darvill quite attractive with that scruff, but you know.)
The only disappointments I have with the first season was the lack of development of Kendra and Carter, and the whole Ray/Kendra pairing that didn't even last. I mean, they did spend two years together when they were temporarily stranded in the 1950s together, but we didn't see any of that so them as a couple just never really seemed convincing enough to pull off. It just seemed rather filler and unfortunately dragged the show, in my opinion. Vandal Savage wasn't exactly spellbinding, either. I'm sure the actor had loads of fun, but the character himself was too mustache-twirly for me to take seriously. I was intrigued by the Time Masters manipulating and controlling everyone by orchestrating everything, including ordering the deaths of Rip's family in order to set the course of his revenge, and I have to admit that was rather a clever way of taking on the concept of time travel. My only nitpick is with how quickly it was resolved, at least from how the season ended it with. Who knows what will happen in the second season, but I do wish there was more of an outcome of the Time Masters as a whole.
Overall: The first season of Legends of Tomorrow was just entertaining and fun, in my opinion. Sure, it isn't perfect as I had previously pointed out the things I didn't particularly favor, but as a whole it was still rather enjoyable nonetheless. I went into this show mostly for Sara Lance, however came out really liking everything else. And although we lost some characters by the end of the season, we will be gaining more in the new season and that will be interesting, to say the least. Plus I have to admit, I'm highly anticipating the crossover with Supergirl as well.