This depends on your purpose of keeping a currency for 6 months.
The big coins in the market are very unlikely to give you big profits, but the big and reputable coins have a high level of safety.
If you invest in new projects, it can bring you high returns, but the risks are also great.
This is why if you want to play safe in the market. You can choose BTC, ETH or BNB. These 3 are quite solid to keep and they will just improve in the next coming months. I am awaiting specifically for ETH this coming month, because of their EIP 1559. It may boost their price if they can deliver what they are supposed to deliver. BNB on the other hand, is still growing because of the projects that are still being created under their platform. For other alts, you need to assess them one by one what is their real deal in the market and in terms of their developments, can they really attract users that will actively use their network?