So you’re new to mountain biking, but may or may not be new to tools. Either way, you want to get started maintaining your mountain bike. These are the very first tools you’ll need to perform the vast majority of repairs. As you get down to more advanced repairs like bleeding brakes, replacing bottom brackets, and pressing headsets, you’ll most certainly need additional tools. For your first year though, this should easily cover it.
Source : Seth’s Bike Hacks