Learning songs is often every musicians/pianists focus. However, to really grow and develop further, a significant amount of time needs to be dedicated to technique. I recommend maybe spending 20% of one’s practice time to technique. Here are some of my recommendations for different levels:
Advanced Players:
Liszt Technical Exercises for the Piano
Pischna Technical Studies
Heller Studies
Intermediate to Advanced:
Hanon’s Virtuoso Pianist in 60 Exercises
Schmitt Finger Exercises Op. 16
Dohnanyi Essential Finger Exercises
Beginner:
Dozen a Day
Hanon for Beginners
~Mary Bellah