First off let me say good on you for wanting to improve and asking how. That's step one. Now, take the advice given above on getting your gear squared away, no loose or dangling stuff but do it for the right reason. That is, it will make you a better diver, less prone to disturb the marine life or sea floor and reduce the chances to get snagged on other stuff.
The notion of streamlining for the sake of speed or even reduced effort is kind of like asking a turtle to keep it's head down to improve its dive time. Scuba diving is not a race and speed is not your friend. In those occasions where you find yourself heading into a stiff current, your skill, ability and primarily your fitness level will make up 98% of how you do, gear selection and configuration only contribute a very small amount of to the overall effort. Don't get caught up in the hoopla. Dive slow, learn some more and enjoy it. Leave the racing to the racers.
The notion of streamlining for the sake of speed or even reduced effort is kind of like asking a turtle to keep it's head down to improve its dive time. Scuba diving is not a race and speed is not your friend. In those occasions where you find yourself heading into a stiff current, your skill, ability and primarily your fitness level will make up 98% of how you do, gear selection and configuration only contribute a very small amount of to the overall effort. Don't get caught up in the hoopla. Dive slow, learn some more and enjoy it. Leave the racing to the racers.