Joachim Raff's WoO. 36 etudes provide a progressive set of technical studies designed to enhance a pianist's dexterity and control. They cover a range of pianistic challenges suitable for intermediate to advanced players.
Develop evenness in scale and arpeggio passages and practice precise finger articulation.
30 Fortschreitende Etüden (WoO.36) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
30 Fortschreitende Etüden (WoO.36) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.