Some supplements do have legitimate mood effects with have some scientific evidence of effectiveness, so it's not all placebos and nonsense. 5-HTP and magnesium are among those, as are omega-3s and Vitamin D. They aren't really a treatment by themselves, but can boost the effectiveness of more established treatments like medication and therapy.

Homeopathy is sometimes used synonymously with holistic healthcare, but they aren't the same thing. Homeopathy is widely debunked as a complete pseudoscientific fabrication, unlike nutritional supplements which can legitimately help. Sounds like this Mood Fix stuff is more the latter. Definitely worth discussing with a pdoc just in case there could be interactions with anything else you're taking, but if not, and it's affordable and seems to help, why not?