I am new to this forum thing but I thought I would give it a  try.  Photography is a hobby of mine but has slowly become incorporated  into my job as a graphic designer.  I am still learning a lot about  photography and how to set my aperature/shutter speed in order to get  the correct exposure.  I have recently been asked by my employer to do a  photo shoot of three owners of a restaurant for our magazine cover and I  am very nervous about it because I am not sure what the lighting  situation is inside the restaurant.  Long story short I think it might  help for me to invest in a external flash.  However I am on a budget and  can't really afford the Nikon Flashes right now.  Is there anyone who  can recommend a simple third party flash that can be mounted on my  camera but also used as a slave later on if I want?  I own a Nikon D5000  so it would have to be a flash that works with that?  Any help would be appreciated.  Thanks!