If I should make a list of altcoins to hold in 2019 then I would add Binance coin, EOS, NEO, Litecoin, Stellar, ETH, and Waves.
Other coins on that list cut be coins like Kucoin, ada, ont, Dash, Nem, but if we go back into an altcoin season, then I think you can pick almost any coins in top 400 and you will make money.
to hold lots of Altcoin you have to be able to focus on all the coins you have, so I think you choose among the best, and not too many Altcoin that you hold because you can't focus so much that you don't use your time well.
choose the ones that are really good and have great potential so you can get good results too.