Hey, welcome to baseball! (join date 2015? weird!) You've picked a pretty good site for fans with advanced statistical knowledge. Generally, average is no longer considered an important stat (it has some value, but not that much). While you can get some information from all stats, the ones I personally tend to use mostly are wRC+ (which is a scale where 100 is exactly average, above 100 is better than average by x percent, and below 100 is below average by x percent) WAR (I prefer fWAR from Fangraphs as opposed to bWAR from Baseball Reference) and wOBA. Here's Tapia's Fangraphs page which will give you a much better idea of what he brings to the table than average.