Buy Bitcoin, its network is secured and you don't have to wonder why people are always suggesting it to have. It's simple because it's the top and if you're looking for a security, check its history.
That's why people are very tempted to invest in random altcoins rather than Bitcoin because of the reward, which this reward is extremely high, there are a lot of altcoins that can be examples of this.
what @hugeblack said above me is a good strategy when investing in altcoins, identify the risks of each altcoin you want to invest and allocate a specific amount for that, don't go all in.