Lobo is right that more samples = better pic/ less firefly's BUT bad materials and/or lighting and no matter how high the samples it wont look better check all settings .....watch lots of tuts ..........and if you have to CHEAT ;-) PBR maybe the new kid on the block but a good old fashioned cheat can save hours

ps to get a transparent background on a cycles render ...on render settings scroll down to film and tick the transparent box have fun