At some point when using Vim, you might find a feature it does not have, and which you need it to have. So now is probably a good time to learn how to make your own scripts for Vim such that you can add this missing functionality.
However, before you start, there are a couple of questions you should consider.
First of all, you should make sure that no one else has already created a script that adds what you need—why invent the wheel again? If someone has created a script that does nearly what you need, then why not just help the developer by adding the extra features to that script and thereby make it work for both him or her and you? This shortens the development time and limits the number of similar scripts floating around.
If you didn't find any scripts that matched your needs, you need to get working on the script. In this case, you should consider from the start whether or not you want to distribute your script to others when it is done. Bram Moolenaar released Vim free...