As a beginner, the main objectives for purchasing your riding accessories are 1) safety, 2) functionality and 3) budget. What looks cooler or more expensive might not necessarily work well for you. Here is the basic accessory kit that you should have:

1. Helmet: It is sometimes argued that riding off-road is actually safer than on-road, as there are no cars to hit you! Nonetheless, the possibility of injury remains and increases as your riding style advances and terrain becomes more challenging. No one should ride a bike on or off road without a helmet. We like and recommended the Giro line of mountain bike helmets. A very good and reasonably prices helmet is the Giro Indicator.
2. Gloves: You need gloves for a better grip on the handle bars (try sweaty hands!) and to protect your hands in case of falling off your bike. There is full-finger and half-finger variety, which depends on your own preference (full-finger gloves naturally offer better protection).
3. Eye-protection: A pair of sunglasses or clear-lens glasses to protect your eyes from the wind and dirt/mud kicked up by your front wheel.
4. Hydration: You need water..plenty of it. Small water bottles in your backpack or bottle cage can often suffice on short rides. However, you will probably want to get a hydration pack (such as the Camelback line) for higher water capacity and almost hands-free use.
5. Repair kit: Go riding with no basic trail repairs kit and your risk carrying your bike on the way back becuase of a flat tire or split chain. A small repair kit should include:
   1. A bike multi-tool or a small set of allen keys,
   2. Tire patch kit for fixing flats
   3. A spare tire tube
   4. A small or frame-mounted pump.

You can either put this kit in your backpack, or get a small behind-the-saddle bag.

There are other accessories of course, such as mountain biking-specific clothing, including shorts, jerseys and shoes. But we are focusing on the basics in this article.