PS: The Moment Musical no. 3 is still quite tricky if you're not used to its challenges (double-notes and ornaments with weak fingers) but is well worth learning.
If you want to go even easier then the Sentimental Waltzes are quite easy and short.
The impromptus are nice but IMO they are too long (and thus require too much work) for the amount of satisfaction you get. For an intermediate I think it's better to go for shorter pieces.