I am hoping for big returns so I'm a bit scared of getting bitcoin since it has been going down in value.
Big returns in any venture comes with lots of risk, especially if you want quick profits. And it
going down in value depends on your angle, the price is way above what it was early this year during the thick of the bear season. If you're looking for long term profits then I would also suggest Bitcoin.
However, do not just; 'get some cryptocurrency', first learn about cryptocurrency: when to buy, how to secure your coins, i.e, protecting your wallet and device as well.