I'm only using 2 right now, Coinbase and Crypto.com. No issues with those 2. That probably gets me 90% of the coins I want to invest in. I've signed up for some other popular ones like Binance, KuCoin, Gemini, Kraken. Some of those were a pain for one reason or another or they have the same coins the first 2 I use have. If one of those places have 1 coin I want, I'm not signing up just for that. There is a good chance that coin will eventually show up on Coinbase or Crypto.com since they add new coins from time to time.
And I'm not a (day) trader or putting in stop loss orders and that stuff like that, right now that's a bit over my head. I just find something I want to buy and buy it at what I think is a good price.
Then I use this for price alerts, the level I'm using is about $4 a month -
https://cryptocurrencyalerting.com/
Pick an amount I want to buy in at, that site monitors those exchanges and sends me an email or sms once it hits my price point.
Then I use this to keep track of my portfolio, it's free -
https://coinmarketcap.com/portfolio-tracker/
Other than that, I'm subscribed to some good YouTube channels with people who know what they're talking about. These all have 100's of thousands of subscribers, many with backgrounds in finance, stock trading etc. A few:
Lark Davis
https://www.youtube.com/channel/UCl2oCaw8hdR_kbqyqd2klIA
EllioTrades Crypto
https://www.youtube.com/channel/UCMtJYS0PrtiUwlk6zjGDEMA
Coin Bureau
https://www.youtube.com/channel/UCqK_GSMbpiV8spgD3ZGloSw
Crypto Jebb
https://www.youtube.com/channel/UCviqt5aaucA1jP3qFmorZLQ
Crypto Michaël
https://www.youtube.com/c/CryptoMichaël
Eddie Moon
https://www.youtube.com/c/eddiemooon
CryptosRUS
https://www.youtube.com/c/CryptosRUs
Those all give opinions on what to invest in.
This is a good how to/walk thru channel. How to set things up, how to use this and that. From setting up an account at various places to setting up a hardware wallet etc.
https://www.youtube.com/c/CryptoDad