Blender is free and open source, and a community favorite in the 3D world.
Go ahead and download any version of Blender 2.80 or newer, it will have automatic GLTF/GLB import and export support.
Feel free to create your piece in the 3D program you feel most comfortable with, and then exporting the final as an FBX or OBJ into Blender
Once you have your file in Blender you can do your last pass of optimizations for export.
We recommend using our preview feature to test your files before tokenizing the piece. It will probably take a few passes on export and testing to get it right.