If you are ready to be more adventurous with your impressionist photography you might consider buying a few M42 lenses.
The M42 lens mount is a screw thread mounting, standard for attaching lenses to the DSLR camera. This was once a very popular type of mount, used in various camera models around the world, so a lot of great old lenses are available at modest prices.
You will need an adapter (usually $5 to $30) to be able to use these lenses on modern DSLRs. That adapter goes between the lens and your camera. You can buy an adapter with or without an optical correction element. Without the optical correction element, you won’t be able to focus lenses to infinity and can only take macro shots. How close to the subject you can work will vary with the focal length of the lens.
There are also manual lenses with no autofocus and no automatic aperture. You have to set focus and aperture manually, using the focus and aperture control ring on the lens.
These lenses create an amazing variety of effects, from a buttery, soft bokeh to a crazy swirly bokeh and very interesting lens flares. Pinpoint light sources such as a flashlight, or any object with a highlighted points, will be transformed into exceptionally good-looking bokeh-balls.
My own collection of M42 lenses is always growing, and I don’t see it stopping any time soon.