@druid The series has a serious problem with quality every season and combined with it trying to be goofy, it makes it hard to watch. I think it goes something like: 1-3 are "good" where 1 and 2 are probably the best, 4-5 completely suck and basically nothing happens, 6-7 are close to 1-2 and I never watched 8 and 9.
Think of it as a sinewave. 1 is zero, 2 is peak, 3 goes down, 4 and 5 are negative, 6 tried to go up and somewhat succeeds and 7 went back up only to have a very underwhelming ending. 7's ending as I remember it was basically the typical "let's make this series longer and reset the progress a volume a two or back" one.
Overall, the story was actually interesting to me and I went through the pain of understanding it, but it was completely destroyed by incompetent story telling after the creator of the series (Monty Oum) died. You can feel the downgrade in the fourth and fifth volume because of that. Also you can't watch it on rooster teeth's website anymore since they went bankrupt and then bought by someone, even though it was always free. The "new" way to get it is through Crunchyroll (I think), or sailing the high seas with a cat.