Any top 11 to 20 alts are worth buying, one or two of these alts can possibly enter the top 10 list sooner or later.
Yes, just always depend on the coinmarketcap.com and the alts that are listed there looks promising to invest but still invest with caution. Though there are some that are newly launched and not listed into that are promising too. But much better if you will first depend to that site which is good to those newbies.