I just connected some cables on my new mobo(gigabyte b75m-d3h) exept these :
chassis intrussion header
SPDIF_O(S/PDIF Out Header)
F_USB 1/2(USB2.0/1.1 Headers)
Is it ready to start without these or not ?
You may want to install the LEDs.
The speaker can be handy to have too, especially if your motherboard does not have status LEDs. The speaker will be used to beep POST codes in the event that there's a problem.
Other than that, you're good to go.