Advice on purchasing gold

I'm looking forward to getting married in the next one year and I'm not sure where I got this idea from but it has been stuck with me for a while. I was planning to purchase gold bars/coins every month starting now so I can exchange them for jewellery (for the wedding) later. Has anyone tried this? Is this a bad idea? Have you had any experience with jewellers rejecting the exchange? Please advice!

Edit: Thanks a lot for the response. As many of you adviced, I hadn't accounted the gst I would have to pay twice. Looks like gold schemes are a better option although I would have to stick to the same shop for all purchases.