What is the minimum amount I can start to invest in bitcoin for decent returns? Which exchange is the safest? Which payment gateway is the best?

I think there must have been like a milllion questions like this now but I’m extremely new to this stuff. I’m not from USA so I’ve been thinking of starting with investing 7$ monthly for the long term. But my friend insists I shell out 200$ in the first month and put 80-100$ monthly thereafter. Just for context, 1$ would turn out to be nearly a 100 bucks in my currency. I also wish to know which exchange is the safest as of now and which payment gateway is the best as in lesser charges and processed payments faster without issues mostly. But i Use Binance mostly
#bitcoinhalving #BTC #Earn2write #SHIB