The answer from the Buddhist point of view is easy:
Whatever you buy, don't get attached to it.
It is not so bad if you lose money, it just means that someone else won the same amount of money.
To conclude, money is just a tool, nothing we should get too excited about.
From an economic point of view:
I'm not too deep into the matter, but I think experts advise not to spend more than 5-10 % for gold, because it is rather volatile.
They advise to rather invest the money into different investment categories, so one can minimize the risk of losing money.