I take it first thing in the morning, and last thing at night. Sometimes also in the day, if I'm feeling a bit knackered. I don't notice a difference except with full/empty stomach. It's better on an empty stomach. There are merits to other forms, here's a fairly decent article https://www.healthline.com/nutrition/magnesium-types

I think the best thing to do is try some, but as mentioned, I've tried them all. Only chloride has had a noticeable effect. If you try it, let me know how you get on!