The first thing I would do is get thorough blood work. Then I would address any deficiencies. Make sure your B-12 and D are tested, TSH, Ferritin (Iron), copper, Zinc & Ceruloplasmin.
After you've addressed any abnormal blood work, you can gather information on various supplements and decide which ones you need and which ones you want to try.
I take about 10 supplements for various reasons. Magnesium is a good one if you're having trouble with cramping/sleeping, etc.
When you decide which ones you want to try, introduce them one at a time to see how you feel and make sure they don't upset your stomach. Some supplements are contraindicated for various health reasons so you might want to work with your primary care doctor.