Should I make a horror Sonic manga of a high school Sonic manga?? of even a dark,evil one?

I would say horror, however that may not cultivate to the tastes of your complete audience. The reason for my answer is that 'high school' sonic can be very difficult to pull off in a completely understandable way (modern high school philosophy and Sonic-world reality just seem to clash). Also, I'm assuming that u meant 'dark, evil one' as part of 'horror Sonic manga', as the two seem to go hand in hand very easily.
Does this help u at all?

How about high school with a dark one!

Definitely a dark one cause that could be like sonics new rival ir something

A dark evil one, with dismatched eyes, blood and claws! Any color would be okay for u to choose from, considering u just need to pick from black, red, of blue. I think this might be a good idea! The name could be something creepy and unique

I think it should be a high school manga.