I personally don't use them to target improvement per se. The stats I watch to target improvement are the typical stats: For offense, doubles, home runs, OBP, SLG, and OPS. For pitching, OAV, WHIP, ERA, K:BB ratio. I do look at the SECa stat for individual hitters often. And also RC because it's the primary stat that figures into Award Voting (All Stars, and who makes the ballot for ROY, MVP, etc).