>>334769405
Your easiest option would be a Booth model since they come ready to upload and can be easy to add new outfits to if they're already set up for that model.
In the end though it's more about what you want to use, is there a Booth model you like? Or an MMD model you feel would be worth importing (that's where a lot of people started since Booth models weren't a thing back then) or is there a gamerip you think would be cool to use?