Magnesium - try UltraMag from Source Naturals which offers a multi blend of magnesium - magnesium comes in many different forms and everyone responds differently to the form -
magnesium and rls study http://www.medicalnewstoday.com/releases/173193.php
Vitamin D levels should be checked since it is symbiotic with magnesium - however studies have shown that vitamin d (without magnesium) may contribute to rls http://www.ncbi.nlm.nih.gov/pubmed/22704399