Their worst mistake can turn out to be following someone without any track record. When an unskilled trader sees another unskilled trader sending some filled images with so many indicators and boxes saying this is high and this is low, take your trades here - and then he takes the trades personally and loses, he also lose trust on others and lose hope in crypto. In copytrading also, it is not good to follow anybody based on their recent past performance but their overall results.
People often think that someone who has already been trading will be able to make better trades than them, and they think this way without even trying themselves and learning much about trading or the market. Some are lazy and some are simply in a hurry to earn money so they skip the learning part and think that they should start earning profits immediately after entering the market which is a wrong mindset to have since things can go very wrong sometimes.
It is much better for a person who wants to venture into cryptocurrency trading to learn the essentials about trading and the cryptocurrency market and practice using demo accounts to check their skills and then start trading themselves, with a small amount initially so that they don't lose a lot of money in case they make a mistake. After some time, they will be able to trade effectively.