Ground poles and cavelettis are Great for All sorts of works with your horse.
I know my mare learned the best when we incorporated ground poles and small elevated poles.
YES! While lunging start with One pole. That's all it takes. The focus to get your horse to stay consistant and not react when something different has come in.
When you have gotten a steady rhythm with your pole, add another appx 6 ft away. Let your horse trot through both.
Keep adding a circle of poles till its a whole circle- more power to ya! Make sure you incorporate transitions and change of directions- this is what will create more muscle.
While riding: start with a ground pole around a turn. Get your horse listening and bending (slight view of inside eye, hold inside leg and keep horse forward) at the turning pole, incorporate transitions. Give a "focal point" to really get your horse listening.
Adding more poles like you see in videos varys on riding level and how well your horse knows where their feet are.
When you have a steady trot thru 8 poles and your horse is staying in rhythm, you are doing figure 8's and changing the patterns of your lateral work- you will notice your horse using different muscles. Keep watching some videos and make sure you understand the spacing of poles too! Good luck :)