Please suggest me... about buying weights....?

It depends on how much you have trained before. I like a combination of dumbbells and barbells so if you can afford it, buy some of each. Think about what you are lifting now, and buy combinations that will work for that, but will also allow room for you to increase what you are lifting. How much you should lift depends on your current level of fitness and whether you have lifted before. If you have not lifted before it would be worth it for you to join a gym for that next three months and take advantage of the services of a trainer. That would probably be cheaper than buying all the weights you would need.