A ripple effect is just what you think it is it goes on and on. Like the ripple effect of a wave of water, it can be huge like in the ocean wave or smaller like when something is dropped in some water. I like the second description better because when that happens it spreads all out from around the point of entry and then keeps extending outward.
Think of the effect someone had on you by just saying "Hi" or "How's it going" with a smile. Or when someone you didn't know let you go in front of them in line. How about the times you've had a chance encounter with someone and in the course of that interaction you both got a chuckle out of something. Doesn't that change your mood? Suddenly the muck that was running around in your brain has disappeared. You're in a different place, mentally. All someone has to do is give me an unsolicited piece of chocolate and I'm in a good mood. It's so simple. Now I'm in a better mood which causes me to be friendlier with the people I come in contact with. I then put other people in a good mood and then it keeps on multiplying - the ripple effect- its random acts of kindness. It's what makes the world a better place