if i want to mine gamecredits an then set difficulty to to 16384 how do i do that ?

i just bought some oldschool mining hardware and hoped i could use it here, i am a new miner. its currently clocked to 11 mhash, what i want to know is if i can set my own difficulty like explained on site ? d=2048 example ?. or what is your lowest difficulty ?. i am using cgminer 3.1.1 for windows ...