HouseBoy, you don't necessarily have to use an agent. I didn't and found a BARGAIN. I am totally happy with my apartment. If your budget is below $2,500, you are better off checking out the classifieds in the Straits Times which are also available online at classified.asia1.com.
The East Coast is great if you have a car. Otherwise, if you are starting out for the first time in Singapore, you are better off in the town area (i.e. District 9 or 10). River Valley is a convenient location if you work at Raffles Place or at Marina/Suntec City.