If you only run one Reddit account with ASB Reddit Bot, you do not need to buy a private proxy. You will need to buy a private proxy when using two or more Reddit accounts. ASB does not work with public proxies.
ASB Reddit Bot runs on an emulated platform similar to the Reddit apps used for Android. Therefore, your Reddit account(s) will be completely safe. The accounts can only be locked if you do not abide by the rules on Reddit.