As you suggest, for those who are new to trading, its best advice to choose the top most coins which are high in trading volume on best exchanges as this will be a safest and the correct move in the beginning. Invest little in the beginning. Choose Bitcoin as the very first one. If you wish to choose coins that are less or equal to a dollar, then choose Polygen (Matic) which is the best choice for now to trade on mid term.
If we are going to suggest newbies then surely we need to give them something solid because we all know it's very unpredictable market and any wrong decision can ruin them which is never been good idea for me if someone asking about coins will just suggest for bitcoin and Ethereum and if they need some more than Litecoin and BNB because currently these are very solid and having very good record in crypto market.
Bitcoin, Ethereum and BNB all are very good use case for long term and short term, so anyone can use them for midterm trading as well these are never been in bad shape even we have very bad crypto market.