I have found an awesome way to get lives very fast which will help you greatly in trying to beat the harder levels later on in the game (Mainly for hard play through) or for getting this achievement.
First of all you need to have reached level 3 "A Zero's Journey" Then reply this episode, Follow the path down past the four walls that are trying to push you over the cliff, Jump up the cliff and grab the free jack (Gold thing) then jump across the cliff and jack the Snipe.
Now, run past next two moving walls(Make sure you do not get pushed off here otherwise you will lose your Snipe).
Next press the B button on the big blue ball, This will give you the chance of getting a free life(The golden apples) And a bunch of Mojo which will also score free lives if you collect enough.
Now jump up the cliff and jack the next monster run past all the little enemy that will start to spawn and across the bridge, you will see a second big blue ball which will get you even more life's or mojo.
Now pause the game and hit "Save and Exit" Rinse and repeat. This is much easier and faster than playing the first level over and over again.
If you find this solution to be unhelpful, please tell me why in a comment and I will update it the next time I'm online.