Choose an potentially altcoins and already known by many people. Like Ethereum, Litecoin, Neo, Waves etc. that's one of example of altcoins that for long term investment. But you need to analyze first the coin, right a lot of altcoins are in a cheap, good to invest.
Long-term investment in those most top coins is safer, we can do day trading at the meantime until the continuous bearish trends over. analyze more coins at this time whether they worth it or not.