You can purchase ARCBLOCK from these places
Go to Kucoin.com
The People's Exchange
Go to Bithumb
Bithumb is one of the largest exchanges in South Korea, allowing users to buy/sell/store Bitcoin and Ethereum.
Go to Huobi
Huobi (火币网) is a Chinese digital currency trading platform and exchange based in Beijing. Huobi was founded in September 2013.
Go to OkEx