You will likely get a lot of opinons. I am a beginner myself so take my advice with a grain of salt. for $300 you can get a Garrett Ace350 which is what I got. It is easy to use, works well, and comes with headphones, a digger and a pouch. If you spend less on the machine itself it means you have money to spend on other things as well. I found I was digging blank holes until I got a pinpointer. I got a Garrett Pro pinpointer, but if you just want to try a cheap one to see if it works for you, Harbor freight has a cheap unit for $17
I found good advice here:
http://www.bigvalleymetaldetectors.com/best.htm but I am sure this could quickly turn into a heated discussion.