If you are interacting on the BNB Chain you will need BNB in order to pay for the transaction costs (gas). Here is a quick tutorial on how to get BNB into your Metamask wallet.
Adding BNB Into Metamask
PLATFORMS AND EXCHANGES
Below are the best options for buying crypto to trade from a Centralized Exchange.
Binance or Binance US (this is the easiest way to get BNB)
Create a free account | Binance.US
The wait time on this may be extremely long so although it is the direct path it may not be the easiest
Kucoin: (if you are in USA & unable to get Binance you may need another platform to use with this such as Coinbase)
KuCoin: Sign Up | Register
How to buy BNB with Kucoin
Coinbase- There are 2 versions of Coinbase. Regular & Pro.
Regular is easier to navigate early on and the Pro version is a bit more complicated but has less trading fees. You can onboard your fiat through regular to get started then start migrating over to Pro when you get the hang of things.