You have to do some research. Canada's Scotia Mocatta is one of the largest volume dealers in NA. I have dealt with their retail store here in Toronto but they also have an online presence. A quick search brought up
this article in Forbes that lists some sources.
Buy from a reputable source. Only buy the easy products - American Eagles, Canadian Maple Leafs etc from trusted refiners. You can buy coins & bars in many different sizes. I even have a 1/10 oz good luck piece that sits on my desk. Keep it in it's original packaging & keep your receipts - both make it much easier to sell, since it has to be recognized & verified before you get maximum cash.
And be aware that gold is a long term hedge & usually not a good vehicle for quick profits. And you have storage costs unless you bury it in the backyard.
Ian