For street riding, I'd try the Sawmill River Parkway or the Bronx River parkway. These are lightly traveled early in the day, especially Sunday. The Hutcheson River Parkway / Meritt Parkway is too busy IMO. I used to ride them a lot when I lived in the Bronx. Just manage your speed well, and they will give you a chance to practice turns and such. Once north of I-287, these roads are even better.
For some light Highway experience, grab I- 684 at Brewster and head north. It used to be pretty light traffic on Sundays, and a good way to get used to highway speeds without all the traffic on other Interstates in the area.
These roads beat I-87, I-95, I-287, and even I-84 and local surface roads for getting some good easy learning in at a reasonable pace (speed limit or a little above) without having to play dodge cage, or getting stopped at every corner by a light.