I googled what the easiest piano concerto is since I'm a beginner. I got Schumann in a minor. Then I went to IMSLP, and it gave me the “easiest piano concerto.” :
Schumann: Piano Concerto in A Minor, Op. 54 by Robert Schumann - Piano - Digital Sheet Music | Sheet Music Plus
Schumann: Piano Concerto In A Minor, Op.54, Second Movement sheet music for piano solo
Clara Schumann - Piano Concerto in A minor, Mvt. 1 (Op. 7) Sheet music for Piano, Trombone, Flute, Oboe & more instruments (Symphony Orchestra) | Musescore.com