Since you are a beginner, try to go for a light racket so that it is easier for you to master your groundstrokes (forehand, backhand). There are many theories in choosing a racket. My suggestion is to get a racket which is:
1. Super light. Around 8.9oz to 9.2oz is great. Try Head TiS6 Supreme.
2. Go for balanced racket or rackets which is less than 5pts head heavy. Avoid head light rackets. Some rackets are heavy at the handle while some are heavy at the racket head. As a beginner, a head heavy racket gives you more room to improve your foundation.
3. 27.5 inches in length. A 27.5 inches length racket gives you a balance of power and control.
4. Oversize racket. An OS racket with a larger sweet spot allows you to hot the ball more easily and since you are a beginner, it will give you more encouragement. Imagine a scenario where you keep hitting the frame of your racket instead of its strings. You'll probably want to give up tennis.
Some racket recommendation:
Head TiS6 Supreme. Wilson Hyper Hammer 5.3 OS, Wilson Hammer 6 OS, Wilson Ncode N1 (if you can afford it).
For a beginner, it is important to get a good racket so that you can get into the game comfortably. Go for a $160 to $200 range. If you have a coach, try to ask your coach to help you buy. They would know people and therefore can get you better discounts. Avoid buying at major retail store like royal sporting house or sportslink. They are more expensive.
One more thing, gripsize. It is super important to get the correct gripsize. Print this out to measure your gripsize. Print out the grip sizer in the wilson [
http://www.wilson.com/wilson/products/sport_home.jsp?FOLDER%3C%3Efolder_id=2534374302525221&bmLocale=en]home page to measure your grip.
Check out
http://www.tfntennis.com for more details. It's a Singapore tennis website.