I think it's great that crystals have such a strong effect on you. If you don't need anything else, that's great.
I wonder if birthstones work at all for the people whose month they match, like your Topaz being for November birthdays. My birthstone is amethyst, and I wear it a lot, but do not notice much. Only quartz seems to help me, and nothing works for me like your topaz does.
My depression is chronic and severe, secondary to my having a slowly terminal illness that has severely limited my life and made me constantly miserably ill for over 30 years. I wish I could find a crystal strong enough to fix that.
I've studied to be a Naturopath, but did not finish due to my illness and also practicing is illegal in the state I live in. Magnesium would help anxiety, not depression. If you are only going to try one supplement for depression, I would go by the seriousness of the depression. If mild to moderate, I'd use a high EPA fish oil, unless you already eat wild caught salmon at least twice weekly. If depression is severe, I'd use D-Phenylalanine, 8 weeks on, then 8 weeks off, then repeat, unless you have high blood pressure like I do, in which case, do not touch it! If you have high blood pressure, you might try a SAMe supplement, about 200 mgs. to start and see if that is enough, since it is expensive. I am assuming your thyroid and adrenal glands have been properly checked first. One of the major causes of depression is low thyroid function, especially if you are female and over 50, and many doctors do not test properly or understand that new normal ranges were put out in 2003 and the labs have not kept pace. I have no idea of your age or gender, sorry if this info does not apply.