I suggest bigger exchanges with good reputation and trust which I think is the most important factor. The others to check: security which is also related to reputation in crypto community, customer support, low fees, good liquidity, user friendly platform.
currently, Binance, Coinbase, and Huobi have all of what you have said...
For newbies, it is highly recommended to start trading on large exchanges with real trading volume so that you are familiar with the user interface displayed by the exchange site. Don't you dare try a newcomer exchange because it is very risky.
Instead of using real money, I prefer to suggest demo versions of crypto exchanges. It will be early to talk about the crypto margin trading but there are demo versions of leveraged crypto trading which can be useful for learning the up-downs in the volatile crypto markets. Even 1:10 leverage is enough to understand the risk management in case they skip the demo version and go directly for the low capital trading.