Earthlings (2005) was life-changing for me, opening my eyes to veganism. A more recent version is Dominion (2018).

But these deal with a gruesome topic. Planet Earth (2006) is more suitable for "favorite". It blew me away, because I've never seen wildlife footage like this before.

don't give more to someone then they give to you

I tend to disagree on that one. Random acts of kindness/selflessness to people, even complete strangers, can bring bonus satisfaction to your life (and sometimes will be paid back). Make it a habit to give to people, when you have the chance, especially if it is low effort.

If you have people around you that just constantly leech off of you, then I agree: don't let yourself be sucked dry.

Now imagine there's an outdoor barbecue and you're a pig and the only person speaking up for you is disregarded by everybody else as a dysfunctional nutter.