Nothing has stable value over long term - dollar and gold can decrease with time too, or rise. So, there's no "saving" without "investing". And when it comes to investing, it's better to diversify your portfolio. For example, you can keep most of your savings in Gold or Fiat (depending on your country), then smaller part in Bitcoin, and even smaller in some altcoins.
In short its the best thing if you are going to do both things. Because if you realize that you need to diversify your money for investing then you shpuld be aware too that you need to save.