ANSWER. Hmmm. Go and get a dictionary and look up the word altruism….
The rule of three that you refer to in your question is a Wiccan belief. Few non practising Wiccan witches believe it. I personally think it’s a load of nonsense. Yes there is a logic that if you put nothing but misery into the world you are likely to get nothing but misery back but that isn’t down to anything special to do with spells or magic, that’s down to the type of person you are. Nice people are likely to attract nice people and happy people are likely to spread and receive happiness. And magic is all about intent. If you do something for someone else with a glad heart because you want to help them then chances are you’re a decent sort of person who will in turn receive help from others. If you cynically cast a batch of spells to help others with nothing but the sole intention to benefit yourself then chances are you’re a bit of a selfish sod and things probably as a consequence won’t always work out well for you.
Sometimes magic is employed for selfish reasons, sometimes its employed for altruistic reasons (did you look that up??). But be clear about the purpose of what you are doing. Spells where your intent is muddied won’t work very well. They won’t backfire with a huge and explosive karmic reaction, you’ll just find you wasted a lot of energy that hasn’t achieved very much at all. A good witch is wholehearted when she casts magic - focused and direct. Cheating magic is a bit like trying to cheat your own will – rather futile.