Racing Sail Options
My previous boat was a J/24 one design racing boat, there are three options to consider for improving your existing set of sails. I'll list them in order of increasing cost.
The first option is to find another boat like yours that is very actively raced. Often owners will sell sails slightly used (less than one season). If your current set is 10 years old, this could be a big improvement. You should expect to pay ~50-70% of retail depending on the condition of the sail.
The next option is to find a local sailmaker. Ask around your marina / yacht club. The guy I used http://www.waterssails.net/home for 5 years on the J/24 would make us 3 sails for approximately the price of two from one of the big name sailmakers. Quite often these smaller guys will be more than willing to get on the boat to help you get it tuned properly for their sails.
The last option is to buy sails in the off season. Quite often you will see the big name folks offering 15-20% discounts for orders placed and paid for in the late fall or very early spring. Make sure to get the rep on your boat to get it tuned properly for your new sails.
Like most things, you get what you pay for, whichever route you go, try to stick with the same source, the knowledge you gain from the relationship you make with whoever you get your sails from will likely improve the performance of your boat almost as much as the new sails.
Good Luck!