Investment in gold bars, logic? Where can I buy them?

One of my friends has suggested to save our money (something between 500 to 1000 Euro monthly) in gold bars. I have just checked it online and it seems we can buy them from Sparkasse (but it seems we should order it first online). We are both foreigners, I wanted to know what native Germans think about it and it you have experience in it, where have you bought it?