I have a friend who only uses the online exchange to earn money. I look at it and understand that this is a very real level. but which asset should I choose in order to start active actions?

Anyone who has small assets in crypto can become a member of a crypto exchange. The volume of transactions matters. you could have less commission on large trades. I also advise you to explore all the possibilities for trading bots. Such software will help you reduce the burden of transaction control.