How much magnesium glycinate should i take with 1000mg of calcium citrate a day (for osteoporosis)?

Generally none: Check w/your doctor. Magnesium can interfere with the absorption of calcium if you take them together. You don't need to replace magnesium unless you're deficient.

Depends: General recommendations are 1:1 or 1:2 or 2:1 ratios of magnesium:calcium depending on needs. I prefer 1:1 or 2:1. For osteoporosis, you also want to consider vitamin K2, boron, and strontium as well as vitamin D.