I am a little bit confused, are you asking about trading coins or good alts for investment? Both are different for me. There is no longer trading, it's hodl! For hodl purpose, after Bitcoin, you should pick the top coins like ETH, LTC, EOS, BNB, LINK, ATOM and so on! Because there is less risk. But yet you should research yourself before investing in any coins, don't follow someone's prediction, strategy, make your own!
i also recommend or suggest ETH,BNB,LTC besides BTC because of their past development
and base in their team behind too then for me this can be trade with day and long term