All participants must give their informed consent to this. We don't want to rip anyone off. Clothing should be trousers, shorts, skirt, shirt, T-shirt, I don't mind. Or beachwear is fine. No nudity, we're not making pornography here.
Bare feet are acceptable.
The usual gloves for boxing. A punch to his face, then cut the action, show her grinning and sneering at him, apply ketchup to his face, then the camera zooms in on the bloody face. Large black and purple bruises can be made using washable skin colourant. The level of violence can be anything that would be tolerated in Hollywood. Look at the Rocky films if you want a guideline for how far that goes.