The first thing you need to do to answer your question is to look into the Cal 28
class rules, if you're going to sail in a class (or if you're going to sail in PHRF and adhere to the specified rating for your boat). I'm pretty sure that class rules for the Cal 28
specify dacron and so that makes that decision easy.
Generally speaking if you want to be competitive you'll want to ditch the furler
and put on a foil. You'll also want at leas
t two jibs...a big genoa
and a #2 or 3 for heavier air. Using a furler
to shorten sail during a race is equivalent to running a marathon in hiking boots given how it destroys the shape of the sail. You'll lose your ability to point pretty much entirely, which is the difference between competing and coming in dead last.
In short, check the class rules which should lay out sail dimensions, inventory, materials, rigging
There's a huge spectrum to racing on the Chesapeake. I've crewed on an old J35 with 10 yo sails, and a Farr 400 which goes through +$25k of sails a year. You might want to just race your boat as is the first season and learn it, focusing on the process and crew work, and save upgrades for later when you're in a much better position to judge what's important and worth investment.
And no, you generally don't want to put composite sails on a furler, although there are some that can handle it.