As you gain experience you will find it is best to keep the fabrication method limitations in mind when you are designing a part. Such as print orientations and how it will paly into part strength . Such as a long item may not be structurally strong enough printed in one orientation vs another Tall thin items printed vertically will tend to snap at layer lines. If the same item is printed horizontally it will be many times stronger with the layers running the length of the item. This is not an issue when injection molded as there are no layers.. Also, over hangs require supports, try and avoid the need for support as they increase post processing requirements and filament waste.
Have fun!