How To Link My Bank Account To Crypto Com?

I was told to go check out Gemini, happy I did. But one thing I’m confused about is this:

If I want to exchange USD to BTC, and then transfer the BTC from my wallet on Gemini to a different wallet (on another exchange which supports GRS), will GRS still pay me back? If not, how do you get money from your bank account into a crypto-wallet?

Also can you explain what a margin call entails for a trader? From what I read yesterday it seemed like an automated script would up the amount of collateral you have by say 40%? Would this increase our tiers even more? Thanks! Could somebody please help me with something very simple…. if i want to buy btc with my bank account but don’t have any bitcoins in it… how should I go about finding someone who will sell me bitcoin for cash —> i.e. using ain’t ain’t here alrighty thank uG’day allSo just got into cryptos last month and found them interesting —> so inspired that “liking” coins on facebook led me to coinmama –> Bitstamp –> Binance… & & & etcCan anybody tell me how/where/why do people buy cryptocurrency with fiat currency…?In other words where should I go / which services exist / or am i missing something ?My goal ultimately would be to use my USD credit card at coinmamma -> deposit via Bitstamp -> trade some