Haiyaa, Giang here

If you're good, any market is profitable. Bonds? Profitable, to a degree. Actively managed stocks/mutual fund? Fairly profitable. Passively managed stocks/index fund? Awesome in the long run. Cryptocurrency? Well you're here, aren't you?

The key difference in them are their risk levels. Obviously, higher risks = higher potential profits. The list in term of safety (usually goes) gold/bonds>=index funds>=mutual funds>=crypto portfolio

To really answer this question, you have to do that age-old thing almost every self-respecting portfolio manager does: determine risk tolerance

So determine your risk tolerance - how much risk can you shoulder? A good strategy is to determine how much risk you're comfortable with, then split up your portfolio.

For example, if you're very risk averse, a good play would be a split between a large percentage in gold/bonds and the rest in index funds. If you're more comfortable with risks, the same split will be index funds/mutual funds, and a small batch in cryptocurrencies.

Determine how much risk you'd like - then it'll be easy to pick.