I bring this question to the bbq gurus of Rusty's... That is the budget I have to work with and I'm wondering what I could find, and if it would be worth it to get that grill for someone who is a novice griller and has never owned a grill.
300-400 will easily buy you a nice grill. Especially if you're wanting charcoal.
This time of year, the big boys, Home Depot etc, are phasing grills out due to seasonal space needs, so a decent gas Charm glow or even a basic Weber, should be available if you're willing to put in a little time checking around.
You can probably get a small Big Green Egg in that range (and maybe even stretch up to a medium if you find a sale or something). I'd buy from a local dealer that you know is authorized for warranty purposes, but the link gives you an idea.