For initial gear advice, I’d talk with your local bike shops, see what they have to offer and take a few bikes for some test rides. I’d also echo what Phonebem said about starting off on a hardtail…not a bad idea at all, but then that’s how I started and I may be biased.
For good trails to ride and people to ride with, I’d suggest checking if your area has a MTB advocacy organization. I don’t know where you are, but in New England, the New England Mountain Bike Association (NEMBA) maintains a webpage of all the trail networks they build or help maintain with listings for each of the 6 states that include descriptions of general terrain and what percentage of the trails are geared toward each skill level, directions, and trail maps. Each regional chapters holds multiple group rides geared toward every level from beginner (never ridden a MTB) to groups of semi-pro riders. Groups rides will help you build relationships with other MTBers who will help you with advice and tips along the way and help you immerse yourself in the sport.