As said above, a single tune now is never the same or even as good as before, as ealry as the next day. Right now, I'm 100% guaranteed there is ALWAYS going to be someone faster than you.
Anyways, I guess there is no harm in helping. Some of the best tunes consist of all minimum downforce (depending on the car), a 1.00 toe angle for grip, racing soft tires, short gears, minimum front ride eight, and max imum ride height in the rear, and lots and lots of torque. You need to be able to push yourself off that line in a hurry. Obviously you need to be fully tuned. But other than that, it's really all about tweaking and playing with your settings consistantly to keep up with your competitors.
One other thing...It is OK to have excess weight from the ballast. If the car is an FR, add soem weight to get and move it to the rear, and add enough wieght that you won't bog down the car, but enough to get more weight on those rear wheels. This will help pin the car to the ground and get more traction.
When handling gears, make sure your first gear is long enough to get you going without spining out, but not bogging down (slow acceleration, the picking up towards the end of the gear). This will cost you time, possibly even the race as the car even in later gears will not be able to pick up enough speed to catch up to your opponent.