If you want to know in a nutshell if it's worth watching the anime: Just don't!
If you want to read the long version, you can expect a little bashing.

This anime is a collection of loud stereotypes of the fighting shounen genre. Without wanting to exaggerate, the story and characters seem to me as if they were conceived within a few minutes. Nothing new is offered. The most successful fighting shounen have managed to stand out from other series by developing their own identity. Black Clover doesn't manage to do that. The successful formulas of these anime are rather copied - only in a bad way. Particularly noticeable are the similarities to Fairy Tail, mixed with a bit of Naruto.

The story is about Asta, who has set his sights on becoming the Wizard King, even though he has no magical powers. This is already strongly reminiscent of Luffy from One Piece, who wants to become the Pirate King, or Naruto's rocky path to the Hokage. His friend and rival, the highly talented Yuno, has the same goal. Their relationship bears similarities to Naruto and Sasuke and Natsu and Gray from Fairy Tail, respectively, though Asta and Yuno have a much friendlier way of dealing with each other, which at least adds a bit of originality to the proceedings. How Asta will manage to reach his goal without knowing magic himself? He seems to have a demon inside him, which makes him special. Naruto's Kyūbi and Kurosaki Ichigo's Hollow send their regards.
As for the setting, it could hardly have been closer to Fairy Tail. Whether you need another fighting shounen set in a world where magic is central? I don't. At least not when the implementation is as bad as it is here.

The protagonists and antagonists are - as you might expect - divided into groups. The good guys belong to the Wizard Knights, the bad guys to a formation called the White Night Eye. The Wizard Knights are divided into several squads. You want to avoid the word "guild" from Fairy Tail. Asta belongs to the Black Bull Squad, which contains the biggest troublemakers of the Wizard Knights. Yuno belongs to the privileged Golden Dawn Squad.

What really makes the anime bad are the characters. I'll even go so far as to say that I've hardly seen an anime that has worse characters to offer; especially considering the large episode count in which it would have been possible to let the characters develop. Asta is just screaming around and seems more like a parody of Naruto and Natsu. And he really is always yelling around, not just during fights. He's always yelling the same thing, too. I can't believe his "Mada da! Mada mada!" (translated: "Not yet! I'm not done yet!") anymore. Yuno is one of the few characters who are normal and don't get on your nerves, even if he seems a bit pale in this bunch of clowns.
Worst of all, though, are the supporting characters. These each have a certain quirk that the whole personality is built around. As an example, I'll take Asta's teammates from the Black Bull Squad. Gordon Agrippa speaks so softly that you can barely understand him. That's it. That's all I can say about him. And that's after 51 episodes. And this gag is repeated ad nauseam every time he appears on screen. And not just with him, but with all the other supporting characters as well. Even worse is Grey, who has a cool character design but didn't say or do anything for the first 40 episodes. There was a bit of a surprise later on, but it didn't impress me much and didn't really further his character development because nothing more was said about it and it didn't even seem to interest his squad mates. Charmy Papittoson, on the other hand, only thinks about food.

I think Gauche Adlai is particularly bad, taking the term "siscon" to a new level. Not only is he constantly thinking about his little sister - which makes him just as one-dimensional as all the other characters - but he also gets nosebleeds, which is usually a sign of sexual stimulation in anime. Here, for some, a certain line might have already been crossed. For me, one of the most unsympathetic and annoying characters ever. After all, the past of him and his little sister was dealt with. And that within two minutes. That did little to really get to know him well and develop understanding for his quirk. One Piece, for example, did a much better job of that. There, a separate arc was dedicated to each member of the Straw Hat Gang.
What's more annoying are certain accents, dialects, phrases and standard words or phrases that certain characters keep uttering. An example of this would be Sekke Bronzazza, who can't help but annoy you with his "Fuhha!" (or "Buh Ha!", depending on the translation). You get the feeling that these flat characters are talking puppets, rattling off their tiny repertoire as soon as you pull the string attached to their backs.
There is, however, one tiny ray of light in this black hole of poor character design: coincidentally, I'm talking about a character named "Light." He is the boss of White Night Eye. Completely left cold at first, there seems to be more to him than meets the eye. In general, I like the villains a bit better than the heroes.

Another minus point is the below average drawing style or rather the lousy animations. I even have the feeling that the drawing style got worse and worse. It's as if everyone involved had no motivation left to put just a little bit of effort into this lousy anime. At times, they didn't even manage to draw the eyes so that they would look straight ahead. It looked like they were squinting. And if one shot makes you think, "Ew," that's saying a lot.

Fights are very important for a fighting shounen. However, these are also boring. But maybe these just leave me cold because the rest of the anime is disastrous and I don't care about the characters.
It's not all atrocious, though. At least there is a comprehensible battle system. Once the mages have developed their skills well enough, they are given a spellbook - also called a grimoire - with a three-leaf clover on the cover. These grimoires already contain a few spells, and blank pages can be expanded with new ones. The mages master various main categories (e.g. Water Magic or Flame Magic), on which further subcategories (e.g. Creation Magic, Binding Magic or Recovery Magic) are built. Creation Magic can create a solid form, Binding Magic traps the attacked person, Recovery Magic can heal people. An example of a main category spell would be Flame Magic/Spiral Flames, which can shoot flames. Examples of the subcategories would be Water Creation Magic/Slashing Sea-Serpent - which can create a water snake out of thin air, so to speak, Water Binding Magic/Sea Serpent's Coils, which creates a snake that wraps around the enemy, or Plant Recovery Magic/Dream-Healing Flower Cradle, which conjures up a cage that can heal injured people. Unfortunately, this combat system is not very innovative and also seems to have been developed in a very short time. No comparison to the jutsus in Naruto, the Devil Fruit and Haki in One Piece, the Zanpakutōs and Hollow powers in Bleach, Nen in Hunter x Hunter, or the philosophical approaches in Tenjō Tenge.
There is a bit of variety, however, thanks to Spirit Magic. Particularly talented mages have a four-leaf clover on their grimoire, which allows them to be accompanied by a spirit creature that contributes even more power. Asta even has a five-leaf clover, which is probably the reason why he carries the aforementioned demon.

I'd like to elaborate on the minimalist approach I mentioned earlier, where you think the mangaka developed the entire story and all the characters during a lengthy bathroom break, with an example from the last arc. The Black Bull Squad set out to find a certain item in a particularly mysterious place. However, the design of this place was incredibly boring. The inhabitants had no particular character design or anything else about them that distinguished them from normal people. Within a few minutes, they also met the least interesting elder of the place, who would present them with the item they were looking for should they participate in a game from which they would emerge victorious. At this point I thought it was going to be exciting, but the game was interrupted shortly after it began because White Night Eye interfered. What followed was a battle that was actually quite alright. In the end, the item sort of fell into their hands out of the blue without having to do anything else. The object itself caused little stir. They simply took it, unimpressed, as if they had just bought a roll at the bakery. No scene looked as if it had been created with at least a little effort.

If you want to watch a fighting shounen, there are plenty of better alternatives: e.g. Dragon Ball, Hunter x Hunter, One Piece, Naruto, Bleach, Fairy Tail, Fullmetal Alchemist Brotherhood, Toriko, The Seven Deadly Sins, Boku no Hero Academia, Tenjō Tenge, Mob Psycho 100, Soul Eater or D.Gray-man. If you have already seen all of these and are looking for something new, you should give Black Clover a wide berth and continue your search.

The fact that the anime has nevertheless received a well-intentioned 17/100 from me up to this point is only because I am a big fan of Fighting Shounen and therefore even this disaster could entertain me to some extent.