I am looking for a budget friendly lens to gift a photographer just starting out. He currently uses the Sony α6400 with an 18-135 lens. What would be a good budget friendly lens to add to his collection? He really enjoys moon shots, as well as night photography.

Would a telephoto zoom lens (e.g. the Sony 55-210mm f/4.5-6.3) or a fast prime (e.g. the Sigma 30mm f/1.4) be better for a beginner looking to expand his collection?