r/AnimeMusicVideos
The r/AMV for low-karma users.
If you want to post shorter (30 second or lower) edits, you can use: r/animereels
"An AMV, typically is a fan-made music video consisting of clips from one or more Japanese animated shows or movies set to an audio track." - Source: Wikipedia (https://en.wikipedia.org/wiki/Anime_music_video)
You can post an edit (in video form) of another creator as long as you tag/mention the original maker/poster. Even if you don't know the original poster, you can still post without claiming their work to be yours.