ok, well since i have an N73, i can def help you out
N73, aint cheap to start with, gotta need 850mhz for N.A., few N series have 850mhz, N80, N75, N73, N95, though N73 is not feature rich as other phones, and still around the $400 range, u might want to check out any decent S60 2nd Ed phone, like the 6620, 6682, and a S40 phone such as a 6270, they are good to start with to get familiar to symbian OS, then u can upgrade to the N series, some N series phones can be heavy, depending on ur liking, N73 is one of the lightest, or you can check out the E-series or get an E50 in the meantime to get familiar with the symbian OS, btw where r u in nA?