How To Begin Creating Your Own Chords
It is necessary to have some experience under your belt before creating your own chords because you will otherwise become very lost very quickly. The ability to play barre chords alongside the basic open chords, for instance, allows you to create original melodies over which you can start varying the structure once you're able to play an entire progression using what you already know.
The ability to play all five variations of the pentatonic scale in any given key also provides you with the knowledge necessary to experiment. For example, let's say you're playing a progression with a G-C-D-C chord structure. Easy enough, right? Well, if you know your pentatonic scales and can use them to play a solo or any kind of melody over that progression, then you will be aware of some additional notes you could throw into a chord to mix up the melody a little and give the riff a spicier sound. These notes you'll be using to create the new chord are notes within the pentatonic scales themselves that are appropriately inserted into the chords you already know. This will allow you to shape and vary progressions at which you're already proficient, which is the first step.
Of course, there is a lot of trial and error involved. Many times, you will experiment with a particular fingering that would seem to create a pleasant sound based on your knowledge of chords and scales, but it comes out sounding rough or off-key. This is just one of the many challenges of creating something new. With enough experimentation, you will discover fingerings and chords with sounds you've never heard yourself produce previously, and you will be able to incorporate them into your existing progressions in addition to using them to create new ones. When you come up with some new chords you like, use each one as the backbone for a new progression around which you can develop a new melody and, potentially, a new song. Doing so will only lead to the creation of even more chords and the further development of your creative, musical mind.
One of the best parts about creating your own chords, however, is that many of the chords you create are already chords with names, titles, and established fingerings, yet you were able to discover how each one was played without looking in a book to find out. This is a demonstration of your own creativity and is a testament to how much you have already developed as a musician! It should inspire you to keep experimenting.