Hey
Either go for Orthodontic treatment, that is get braces. This will take from around one year to one and half years.
Another option is Veneers, which is like getting a crown but just in the front side to cover the gaps and also it can give you good contour of the teeth. Also known as Smile Designing. This will take a week or two only.
As of the cost, conventional ortho treatment (braces) may cost you anywhere from around 25000-45000 depending upon type of the braces that is metal or ceramic, and higher for the invisible braces.
Smile designing cost is a lil high too, you can visit your dentist and she/he will tell you how many veneers you need for correction and accordingly the cost.
Next Steps
Visit your dentist.