The goal of NetGuard is to function as a Firewall to limit apps ability to phone home without consent. The host file feature will block most in-app advertising and provide some protection for web browsing. Ads within facebook can be blocked using custom host filed within Ublock/Umatrix. I dont know about ad-blocking within the FB app itself.
Generally, you should be using Firefox, not Chrome, with Ublock and/or Umatrix installed to maintain control of your web experience. FB web interface can be used and ads generally blocked. Reddit's native ads are served directly via first party URLs so it is tuff to block. Reddit's made changes for the advertisers and their new UI is meant to popularize Native ads.
