I am glad you are enjoying reading and want to write something yourself! I always encourage anyone to try their hand at writing a review.
The Steam review system is flawed in its own way, because you have two options, to recommend something or to not recommend something. So one thing I always think about is would I tell my friends about this game and is it worth their time, that usually forms the basis of the opinion.
The other embellishments are just that, I find that I enjoy reading reviews with a lot of detailed information, so that I have gravitated towards extensively describing my thoughts about a game.
I used to do more technical reviews, discussing a lot about the actual gameplay and mechanics, but I find that when I read someone’s review, I am looking for their personal opinions and their emotions and feelings after trying out or completing the game, so I have been gradually changing my style of writing to be more personal, more feelings rather than technical.
If you end up finding an indie title you thoroughly enjoy and wish to review, I think it’s perfectly reasonable to share it with the rest of the IndieGems group. In fact, I am thinking about starting a thread there for users of the group to share their reviews as well.