You don't necessarily need to buy an expensive laptop for crypto stuffs purposes. A mid-range or normal laptop would suffice for trading or other activities. However, I would advise against storing private data such as seed phrases, private keys, and personal documents on it, as it could be susceptible to hacking once connected to the internet.

The best approach would be to purchase a new, inexpensive laptop and keep it air-gapped, meaning it is never connected to any network. Alternatively, you could repurpose an old android phone as an air-gapped device, but it should be thoroughly cleaned (formatted and free of viruses and malware) before using it to store your wallet and sign transactions.