Advice on making engagement ring

So I plan on proposing in a few months and wanted to make something special for her after I saw a video and metal casting with sand. I have a 3D printer and some experience with design so I thought id easily be able to make a mold with the sand but I’m realizing my design is probably too complicated for sand casting(picture below) would you guys recommend I simplify the model and then add the details with a tool after or is there a way I can make a mold out of plaster I should try? I still need to clean up the model but you get the gist. Any advice would truly be much appreciated I can’t stress that enough