There are many top coins to have in ones portfolio. Users can check coinmarketcap to see different kinds of altcoins to buy. Based on my own choice i will love to select the Top 15 in the cryptomarket i mean in coinmarketcap. The likes of BITCOIN, ETHEREUM, XRP, LITECOIN, EOS, BNB, MONER, XLM, and TRON. These sets of altcoins will be very good to have in ones portfolio
Top coins will not leave the same ROI as the low marketcap altcoins, I prefer to add more low marketcap altcoins from the cheap prices thanks to the bear market.
I would add IOTA.
It is cheap atm, has some advantages, like no transaction fees, has a large community,
a lot of well-known partnerships and if the coordicide works, there's a good chance of a price increase.
I have participated in the IOTA token sale and their development is really slow compared to the alternative projects. The large community doesn't mean anything unless they wanna to spread their next success in the crypto industry.