I personally use:
Coinbase & Binance as my main source.
My sources for trading Altcoins is a few groups which I follow carefully. they are sharing crypto picks every few days. This business is a little bit risky and you have to make sure that you are following a legit group . you can use Smartoptions platform to support your research in order to find a crypto signals group that you can actually benefit and profit with. Here you can read a detailed analysis about the TOP 10 crypto groups.
https://smartoptions.io/telegram-crypto-signalsI hope it helps.