All four 9 20 50 200 EMAs to save indicator space and have the most reliable, recognized and respected EMAs. For day trades i consider 9 and 20 EMAs pullbacks on 5 min charts when in overall uptrend . 50 EMA determines if in up or down trend by being above or below (50 EMA was be sloping up or down. 200 EMAs great support and resistance along with the slope of these EMAs are telling a strory, I also use EMA Boillinger Bands along with TTM Trend, Wave A & B , MFI, Volume Weighted MACD, VWAP, and Stoch RSI