Johann Baptist Cramer's Divertimentos are didactic pieces designed to develop technique. They showcase clear Classical forms and balanced melodic lines.
Focus on consistent articulation and graceful phrasing in the Alberti bass accompaniment.
3 Divertimentos (Op.13) is rated Henle level 2 of 9 — beginner repertoire, roughly ABRSM grades 2–3. In the RCM system it corresponds to about level 3.
You should be comfortable at Henle level 2 — meaning you can already play level 1–2 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 3 Divertimentos (Op.13) lasts about 10 minutes.
3 Divertimentos (Op.13) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.