Learning to ride over jumps should be gradual. Ground poles and cavaletti are a great way to learn skills like steering the horse straight to a target, training your eyes, and working on your balance and position when the horse adjusts the length and height of steps. For horses, these are excellent for learning footwork and improving strength and balance.
Ground pole and cavaletti patterns are endlessly available online. Start with walking and trotting over single poles laid around the arena. Build up to circles, serpentines, angles, and lines of poles set to specific distances between each other.
Cross bars, or cross rails, are an ideal jump for beginners because the lowest point is the center. You can build a crossbar using cavaletti or jump standards with jump cups.