I have used a PiHole ever since I learned that LittleSnitch resolves DNS queries (to IP) before the dialog prompts whether to Allow/Deny a connection to the unlisted host. It is an added bonus that I can route my entire subnet to the local PiHole, which prevents rogue software/OS/devices/phones from initiating undesired connections. If you know how to make a few simple IPfilter rules, you can even stop hard-coded devices (e.g. smart TVs) from phoning home with internal DNS IP addresses — all you have to do is capture all DNS queries, IPs included.
Simply blocking pagead2.google.com and googlesyndicate.com will remove 50%+ of website advertising. ReGex rules allow for ads.* (etc.), and these rules apply on your entire local network. For an added bonus, you can then use your local PiHole to resolve DNS queries remotely (e.g. from your phone) — just all around an incredible product!
/r/PiHole
