Like around 2011 to 2015? Before it became available on major exchanges?
Initially it was person to person and later we saw exchanges coming up. Right now it's very easy to buy from exchanges but it has also compromised the anonymous nature of bitcoin. The real aim to bitcoin was p2p trading and no middlemen.
That is true. In the early years, from 2008-2011, transactions usually based on p2p, what was the true purpose of bitcoin - to become a p2p currency. However, nowadays, bitcoin main purposes are holding and trading. It helps many exchange to be existed and earn money by luring people to participate in buying, selling, stacking bitcoin
Some of old exchange I have found, they were mentioned in 2011 on a post of this forum: btcex.com. But it seems it has ceased to for many years
One of the first currency exchange's posts of Bitcointalk:
https://bitcointalk.org/index.php?topic=3400.0