Requesting currency exchange on FIX-Protocol

I need a bit of help, I'm new with this protocol and kind of lost, I need to retrieve a currency exchange price (USD/LOCALCURRENCY) with this protocol and kind of stuck, this is my current flow:

My_APP                              |       FIX_SERVER
------------------------------------------------------------------------------------
LOGIN 35=A                          >
                                    <       LOGIN_OK 35=A
MarketDefinitionRequest 35=BT       >
                                    <       Definition 35=BU
MarketDataRequest 35=V              >
                                    <       MarketDataIncrementalRefresh 35=X
LOGIN_OUT 35=5                      >
                                    <       LOGIN_OUT_OK 35=5

The messages 35=X (I request 269=0 and 269=1), does seem to be want I want, but they're delivered not as quick as it supposed to be and not even sure if this is the right area (market data).

Can anyone give me a bit of light on this?.

Thanks.