Filing a patent application earlier is generally better than filing a patent application later.
This is because the person who first files a patent application is awarded the patent. In other words, if two people file a patent application for the same invention, a patent is awarded to the person who first filed his/her patent application.
Another reason for an early filing of a patent application is because one is planning to disclose the invention to a third party, such as an investor or manufacturer. Doing so can avoid disputes over who first had the invention.
A further reason for an early filing is because the invention is going to be made public, such as being displayed on a website. A public disclosure before a patent application is filed can result in the loss of patent rights.
However, a patent application cannot be filed for a general idea. The patent application must include enough information to enable someone else to make and use your invention.
On the other hand, one does not need to have a working prototype to file a patent application. But, one still has to have developed enough of the invention details to show the invention in drawings.
Therefore, if one can describe the details of the invention in words, and show the details in drawings, one can file a patent application on the idea.