This entirely depends on your convenience – if you have enough time to spend, it may be better to search, choose a property and purchase it directly from the builder. The advantage with this route is that there are only two parties – the buyer and the seller.
You have a direct point of contact, which you can use to clear all your doubts. He may also be useful in the future. You are not required to pay a brokerage, which is an additional cost over the price of your property; and, if you negotiate well, then the builder may give you a better price.
On the other hand, if you do not have enough time to spend looking for a property, then you can choose a good broker to act on your behalf.
Both options are viable, but contacting a person who has decent exposure is important. In order to find a good real estate agent or a real estate company having a good reputation, check the real estate websites. A real estate website contains all the details related to real estate; like types of properties, real estate agents, real estate companies, etc.