Most people have already commented on the question you asked about commission, I'll just make a few comments about this:
If I buy a bitcoin a bitcoin for 10000 dollars, and sell for 10200
Obviously I have gained 200 Usd.
It is not so simple to buy $10,000 and sell for $10,200 and make $200 profit. Let's take yesterday's example.
Yesterday the price was $11300 and then dropped to $ 10900 ... imagine if you bought $10900 why would you think the price was too low? Today the price is $10400. If you will enter this crypto market? so I suggest you read the very news and learn technical analysis and fundamental analysis