Here is a complete list of lifts that we (people on this forum) have made:
https://www.instructables.com/id/The-Official-Guide-to-Knex-Ball-Machine-Lifts/If you're looking for something easy, I would suggest the chain lift. It requires special chain pieces.
If you're looking for something interesting but sturdy, I would suggest a helix lift. It requires special tubing.
Another sturdy lift is the Up and Down Lift. I made a version with a much lower piece-count that I can share with you.
If you're looking for something aesthetic (but big) I would suggest a wheel/ring lift.
If your lift is only raising balls 2ft, I would suggest an arm lift.
Almost every lift requires the ball to start a few inches above the ground, so that the lift can reach underneath the ball.