I take 250 mg of magnesium daily, with Vit B and zinc. If you do a Google search on "Daily dose magnesium migraine sufferers" it will throw up a lot of interesting articles on this subject - all of them positive.
re: Triptans: the most often prescribed in the UK, Sumatriptan, is called Imigran over here, but no doubt has different names elsewhere. It is extremely effective at aborting a migraine, indeed it has transformed my life, but I am aware that often, the day after I've used it, the migraine returns and this "rebound" headache often leads to another pill being taken.... and so on, sometimes for days and days at a time. This rebound tendency is certainly understood as a possible unfortunate pattern by GPs here in the UK, but the drug remains the essential anti-migraine medication. Indeed I wouldn't travel anywhere without it.
But the magnesium does seem to offer increased resistance to migraines, and I noticed the difference immediately.