Casual users dont get on private trackers hehe. Joking, some guys were posting site that tracks when private trackers have open invites, hope someone will link again. Some trackers are almost impossible to join or keep up with their rules, but like torrentleech should be easy enough. Ive never used usenet since Im on private trackers for years, but I bet someone can recommend one here.
You can look for older redit posts about recommendation for both, but first decide what contet you are aiming for. Some trackers are just for movies, some are focused on music, but there are also general purpose trackers like torrentleech.