Traditionally high magnesium plants have been magnesium-depleted by magnesium-depleted soil. Go for them, but also get a magnesium supplement or two. Orally, just try to stay away from magnesium oxide - it's hard to digest. Any of the other are okay - except orally, they go right through you. Uncomfortably so if you take too much. You won't OD (can't OD, what you don't use goes out), you'll just need to be near a bathroom. Very near...
Solution is to limit the oral dose to a comfortable amount and then also take it in through your skin, "transdermally." Make "magnesium oil" out of water and magnesium flakes, and just spray it on and rub it in, or soak in epsom (magnesium) salts and warm water - feet, legs or your whole body.
You'll sleep like a baby.
bfl