Teachings come from Eric Muathe's MACD playlist on youtube. I highly recommend.
You will note that the most recent buy signal was a good one because the cross occurred outside of the trendline. We know this tends to be a good signal from back testing.
Always draw your trend lines when using MACD. Sometimes you will that they are not that helpful. For example I drew a trendline from essentially the start of the MACD and connected it to several points as it rallied. It had a trendline break which you could have sold because of; But it was not that strong of a signal. You would want to stay long instead. It got you out one week before the bottom (from 65 to 55).