Cost may be variable from 5,000-75,000 Basing on the treatment plan Either  1)cement to fill the gap 2)crowns (metal ceramic to all ceramic)based on ur financial budget 3) Orthodontic treament (metallic or ceramic or invisible aligners)

At your age braces is a good option as it is non invasive and gives permanent solution. If gap is small it can be filled by ceramic fillings as well. Crowns or veneers will involve slicing off your original teeth.

1-If gap in front tooth then u can go for crowning (FPD).it will be cheaper n permanent treatment.cost will depend on no of tooth...like per tooth crowning 3000/-rs . 2-if spacing is in all tooth then I will suggest u braces treatment (fixed orthodontic treatment).it will take time but permanent results.charge20000-25000/-rs 3-if u r more conscious look wise n u have more budget then u can go for Invisalign treatment (best orthodontic treatment without visibility of wire).cost 60000-80000/-rs.