You should join the local mt. bike club - CLIMB. Chances are pretty good the trails you all are riding were built and maintained by CLIMB. The Face Book page is very active as is Long Island Mountainbikers on FB. CLIMB usually has beginner rides first Sundays, Bethpage, Edgewood, Calverton and Eastport are the usual rides. Club Membership gets you 10% off at a lot of shops, I purchased 2 bikes at Brands using my discount, saved me many years of the membership dues.
https://climbonline.org