Welcome to the Hub! Accessories contain all manner of items - but one non-negotiable would be a decent helmet! At your price range, you can find a fairly decent entry level mtb - which will do everything that it needs to do, without breaking the bank. Take a while to get into it, and then decide if you want to spend more money, and how - going forward... A second alternative, would be to go 2nd hand. Again, at that price-range, you could probably pick up a slightly older bike, that is obviously a bit more used and battered, but one that might have better components on it... Before going this route, however, get educated... Spend time on the Hub, trawling through the search option. Your question has been asked over and over again, with a multitude of responses, that mostly boil down to the same thing... Start buying cycling magazines, check out mtb websites, and pick up as much information as possible about the components, frames etc., as you can... once you've done all of this, you should be able to start identifying why it's not such a good idea to hit the trails and major downhills on just any bike bought at Sportsman Warehouse... You'll then also be able to monitor the classifieds section, and start getting a sense of what constitutes a good deal/fair price to pay, per type of bike... Good luck!
