Teresa Carreño, the famed 'Valkyrie of the Piano', composed this ballade with a focus on deep expressive weight and lush Romantic harmonies. It exhibits the virtuosic elegance expected of a world-class performer-composer.
Achieving an orchestral sense of color and voicing in the dense chordal sections is the primary technical hurdle.
Comparable difficulty and character — good candidates for what to learn next.
Ballada (Op.15) is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 8.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Ballada (Op.15) lasts about 6 minutes.
Ballada (Op.15) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Liebestraum No. 3 in A-flat major by Franz Liszt, ...E nada mais! by Hekel Tavares, Ballad Op.2 by Tivadar Szántó — see the full similar-pieces list on this page.