Moving armature deforms mesh

Greetings guys and gals!

I’m pretty noob at Blender and trying to learn as much as i can from different tutorials. My current project is to import some models from the videogame League of Legends and rig them so I can pose them and later export them so I can 3D print them (if you are wondering, no, I’m not going to sell anything. It’s just a hobby I enjoy).

So far everything is going well until I use Armature Deform with Automatic Weights. The mesh of the model deforms way too much when I move bones with the Pose Mode, hopefully this gif explains it a lot better:

https://imgur.com/oWIPH6x

I read that this usually happens with Automatic Weights and that I can use Weight Paint to adjust this. The problem is that a few vertex are still being dragged even after I used the substract paint.

https://imgur.com/cOnjQD4

Also, there’s this tip of the chain at her legs that for some reason decides to move as well (I suppose it’s probably because of the same reason).

https://imgur.com/jNguVsd

Do you know what can I do to fix this? Please consider I’m a total newbie on Blender, so a detailed explanation is much appreciated :slight_smile: (I can also upload the file if that helps!). Thanks!