To add variations you can replace each degree of the scale with another chord called the secondary dominant.
On Scaler to find the secondary dominants go to the the MOD page,:
Having decided on the key you are using (in this example G major scale so the key is G)
go to the MOD page, and slect secondary scale from the drop-down menu.
Then select your key by clicking on it for the secondary scale. Because my original key was G, I have clicked on G again to display the secondary dominants.
Hope this helps
PS If the pitch of the secondary dominant does not fit your harmony try editing the chord on the Edit page