It's about a school for magical duels, with a brainless skirt-chasing protagonist. That sounds like a reason to avoid it. There are lots of shows like that. This one's much more palatable than you'd think, though, because:
(a) the protagonist's female and there's no harem dynamic
(b) the show's not actually that interested in its battles. They're a relatively minor part of the series and often we don't even see the fights, instead just hearing afterwards that someone won or lost.
Instead the show's more about friendship, comedy and joining school clubs. Our heroine is Eruna. Is she intellectually challenged? Does she do ridiculous things? Yes, all the time, but that's part of her charm. She's as shallow as an evaporating puddle and she chose Mikagura Academy because its brochure had a photo of a hot girl, but she's also explosively energetic and people-oriented. Show her a cold, condescending Jekyll-and-Hyde girl and she'll love-bomb her into becoming her new best friend. Throw her into a battle with no weapons and she'll just run around like a lunatic until she's won. Make her spend every night in a sleeping bag in the corridor and she'll start wriggling around adorably in it, like a bouncing caterpillar.
Eruna's the kind of person who seems incapable of not loving everyone. She's not wired for anything else. Admittedly she's also likely to be pursuing them sexually (if female), but in a goofball way that amounts to nothing more than a few seconds of being a dirty old man. She couldn't be more harmless. She never takes anything personally and believes that everyone should be happy and having fun.
The show's about its cast and their evolving friendships, really. Occasionally there are magical battles, since this is a magical school and that's been deemed part of the students' training. However these are endearingly eccentric (e.g. students fighting with music, or with calligraphy brushes as big as themselves) and almost everyone regards them as a fun exercise. Students who get serious about trying to win are weirdos. The supporting cast includes:
BIMII = a magical flying cat who's apparently one of the school's teachers, but immediately glomps on to Eruna and makes himself her sidekick. Fortunately it turns out that he has a reason for this.
SEISA = Eruna's main lust object and a broken bird who keeps herself at arm's length from everyone.
KURUMI = Seisa's rude maid who has a harsh (but fair) opinion of Eruna's intelligence.
SHIGURE = Eruna's cousin, who's flamboyantly in love with her and won't shut up about it. Ludicrously overdone wooing appears to be a family trait. Unfortunately for him, he's male.
...and lots of other students, usually identifiable by their clubs and tools. (It's a school rule that everyone has to belong to an after-school club, which is how they organise their magical battles.) The drama club are animal-themed. The Astronomy Club member can shoot stars from his telescope, the Flower Arranging Club member has plant control powers like Swamp Thing, etc.
Not to be confused with Mikagura Detective Agency, which is a 2004 pornographic OVA. Eruna would be interested, though.
I like it. It's lovable. I'm amused by touches like Usamaru disappearing into a world of delusions in ep.5 about Azumi Sagara, only to get such a shock on meeting the genuine article that later he'll be in mortal terror when his romantic fantasies seem in danger of coming true. It's a low-pressure show, but that's its charm. It would be easy to imagine this series with a conventional light novel protagonist (and there are indeed some light novels), but Eruna is far funnier and more distinctive. There's not enough to it to justify too many expectations, but you could do a lot worse if you're looking for a smile and some fun.