I made a low poly model and I parented the Rigify armature using automatic weights. i It deformed weirdly and I doubt it's my topology since it's very basic. I used solutions that worked with my other models before, I applied all transforms, I merged by distance, and even flipped the normals. Now it won't move at all once I parent it again. I don't know what to do.
Your model suffers from a few common problems:
the origins of the armatures (rig and metarig), and the mesh is in the center. The origin is the little orange dot. This is will place the root bone of the rig (the big circle with the arrows) at the hips and your character will be sunken half into the ground. Move the metarig the mesh up so they "stand" on the XY-plane, the floor. Apply the Location to set the origin to (0,0,0) and re-generate the animation rig so the root bone will be placed correctly.
if you enable the Face Orientation overlay you will see that you have flipped normals. Red means backside. Using Alt+N > Recalculate Outside in Edit mode does not work because there are loose faces (hair strand, belt, cloth, bootlegs). So you need to fix it manually. Select them and Alt+N > Flip them.
Note: If you plan to export the model to a game engine keep in mind, that the backside of the faces is not visible. To be able to see from both sides you need to duplicate the faces and flip them. Inside Blender, you don't need this.
- Now you have fixed this, the Automatic Weights calculation no longer works because you get the infamous Heat Weighting: Failed to find solution for one or more bones error. That's because the hair strand and the loose fabric parts of the blouse intersect with the head and the body. To fix it select the bad faces (screenshot above), and separate them with P > Selection. It will create a Body.001 mesh. Switch to Object mode, select both body meshes and the rig last to make it a parent with Automatic Weights (Ctrl+P). Blender now can calculate the weights and you can join the body meshes with Ctrl+J if you like.