jQuery 'Manual' Form Validation and Random Array Output

jQuery 'Manual' Form Validation and Random Array Output

My project consists of 3 parts. 

1. Enter 3 pieces of information via a form
2. Manually validate the 3 pieces of information have been entered
3. Output random value from pre-populated array

For the manual validation I would simply like to verify that all fields have a value. If they are blank the user will be prompted with a specific error message based on the field. (Enter a first name, enter a middle initial, enter a last name)

Once all 3 values are populated and the user clicks Submit they will be prompted with a popup containing a random value from a pre-populated array. 

My code is here - any advice would be appreciated.