What sympathetic or echelon of cement do I use to produce concrete garden ornaments? When I went to Home Depot they asked me how masses...

When I went to Home Depot they asked me how masses "rocks" I wanted surrounded by the mixture. I would think none since I want the surface of the garden knick-knack smooth so I can paint it.
Pruning leaves and pseudo bulbs on orchids?
Answers:    I would also recommend a mortar mix as you're not looking for any significant structure strength.
If you do use a concrete mix, you can get the lowest structural strength they hold available (should be cheapest). Your local ready mix plant may also be feeling like to give you some remaining returns out of a mixer truck.
Be sure to rod & tap or shake your mold properly to ensure consolidation so you don't have rocks showing on any surface. If you post the dimensions, I can suggest a little lifts and strokes for rodding as resourcefully as rod dimensions, or vibrator specifications and technique.
Roughly, how various can of hose down does...
You want to use portland cement, and you have to enjoy rocks in it for strength. Once the cement have set completely (will likely help yourself to a few days, depending on thickness, humidity, etc). Then you'll want to trademark it with a concrete sealer to hang on to the elements from deteriorating the concrete over time.
Of adjectives the cleaning you enjoy to do...