Dryad of the Ilysian Grove and Imprisoned in the moon
Your description has the correct result. This looks like the interaction with Magus of the Moon.

The steps are different though.
 1. In the layer 4, Dryad becomes a land. Then its ability gives it all basic lands types (and the associated mana abilities). Dryad's ability is applicated second because it depends on Imprisoned's one.
 2. In the layer 6, Dryad loses its printed abilities and its additional mana abilities but gains "{T}: Add colourless".

No timestamp order is involved.
As a bonus, if you care about land types, Dryad still has all of them.