Best exchange to trade you could consider Binance or Kucoin exchange.

For altcoins to invest in, since you are a newbie, I would advise you to pick and watch over a few coins in your trading. A list of my top picks are below:

You could look out for
1. Cartesi $CTSI a leading blockchain project dedicated to providing the tools needed by devs in the creation of scalable DApps. Cartesi is the operating system for scalable DApps.

2. Atomic Wallet $AWC I can say is one of the best non-custodial asset management out there.

3. Algorand $ALGO is a permissionless blockchain for borderless economy. Great techs. Algorand is the world's 1st open-source, unadulterated proof-of-stake block-chain innovation, that facilitates the improvement of scalable, adaptable blockchain.


4. BLuzelle $BLZ a completely decentralized, secure,scalable database service that is designed for the purpose of assuming proper security of users data.

Take a look of each and every one of these coins and make your own researches as well. You'd be glad for making the best trades with them.