How many chords do you need to create a piece of music? Would you believe that it does not really matter and that whole pieces of music have been created using just one chord? For example, if you play a D minor 7 chord, you could use the bass note D to create a drone effect and anchor the whole improvisation. It could last for a few seconds or many minutes.
The important thing was were you in the moment when you created it? If you were, then it will be a good piece of music. If you were not it will be notes in the air without communication. What communicates is your feeling. It's your feeling that gets across through the notes. The notes themselves are meaningless if you are not present behind them.
I usually do not use more chords than 4 or 5 when creating. I use the chords of a certain Key, for example A major and stay within that key until the piece is done. I may change to a different key, but I will always begin with the intent of staying within one, always keeping the possibility open for change. Remember the power of limits, especially in music.
When you have too many choices it can be overwhelming and will stop you from being able to go forward. That's why learning to play in 4 and 8-bar phrases is important. It gives you the limit of chord changes. New age music is mostly a static music meaning that the chords do not change too much. In fact, you can have the same chord going on for 8, 16 and even 24 bars or more. The amount of change is dictated by personal taste and that you will acquire after you freely experiment with the music.
Remember that attitude is the number one thing. You must allow the music to tell you where it wants to go or you will most likely freeze up and stop the forward momentum. That's why I always tell students the principles for creativity must come first. Without that you are really starting on shaky ground.
So, do not worry about how many chords to insert in your music. For a good example of chord changes, look at my book "New Age Piano Made Easy." It's filled with 84 exercises completely comprised of different chord changes in all 12 keys.