This show is a so-called magical-girl-Anime. That means the main character is a girl who stumbles into a magical item, mostly a magic wand, with magical powers. That means the girl doesn't change into a magician and has no powers without the magic wand.
This anime is a spin-off of the popular Fate franchise and uses a lot of characters from Fate/night and Fate/zero. I must add that the mentioned animes are not about magical girls. This show tries to press more than a dozen characters of the mentioned shows into the simplified magical-girl structure of this anime and fails to do that in some situations. For example, in the beginning, Tosuka is a magical girl, but she is a magician anyway. Other characters are put into an artificial family set up around the main character Illya, but it doesn't make sense. While Illya had a heartbreaking story in the shows mentioned above, she is the magical girl in this anime and becomes a simple schoolgirl.
Too bad this anime misses creating a justification for itself in the first season. The fighting scenes are good, and the speaking magic wands are funny, but there is no exciting content outside the fate references. The creators only had to fill ten episodes, but they already had to use cliche stuff like characters trying maid costumes, women comparing their bust size, bathing scenes, etc. In opposition to the opinion of the creators, the anime audience is not necessarily into such stuff. The anime got dull moments, which sometimes take up half of the show.
It isn't easy to rate this anime. The viewers of previous Fate animes shall be recruited as viewers. But as such a viewer, I am pretty disappointed about the magical girl stuff and the simplifying of many characters. Also, this anime takes the easy road and misses to tell its own background story while not adding something to the franchise. Therefore people new to this franchise will be a bit confused and won't understand all the references to the Fate universe. Consequently, this is an okayish anime, which you can watch but won't miss anything if you are not doing it.