Chords, the lifeblood of song.

You must learn the circle of fifths in order to become a good musician.  You need to move from and to different keys on the keyboard or fretboard.  It is important to practice different hand positions on any instrument.  You have to be careful about which chords you use.  Here's the basic pattern for the circle of 5ths.

1-->3-->6-->2-->5-->1

You can also move in thirds as is done in the first chord change of this passage.

As you break it down into major and minor keys. Remember that the majors and minors of each hand position are different major and minors.  Let me demonstrate by using capitals for major hand positions and lower case for minor hand positions.  These are the two hand positions.

I-->iii-->vi-->ii-->V-->I  for major keys

and 

i-->III-->VI--> flatII-->V-->i

This is the circle of fifths.  Know this and internalize this.  It will improve your music.  You can also use elisions to the 4, and you can use any individual portions.  Your music should be as varied and interesting as you can make it.