So you have hills where the 36/28 is inadequate? If so, an 11-32 cassette would help, providing that your RD has an extra 4T of wrap capacity. You might have to look up the exact RD model to be sure. The next step would be a 50/34 or 48/32 crank. Those don't require more wrap capacity. FSA isn't good at listing the chain ring bolt circles, so it's hard to say whether just new chain rings could be purchased or a whole new crank required. With a 48/32 you also have to be sure that the FD can drop low enough.