Craig's guide to buying classical music, 2019
Go to a record store (online will do but a used record store works better for this)
Head to the classical section. ( They're usually not that many CDs)
Find any on the Naxos label and pick those up.
If any other discs look interesting (performers you have never heard of, composers you haven't heard) pick those up too.
Listen to them, preferably with headphones.
Congratulations! You now know how to buy classical music.