This question covers a lot of ground. Let's assume you want to know what it takes to kill a moose in a legal manner. The answer is in your hunting area's game laws. Generally speaking, you have to have a valid hunting license and a place where you can legally hunt. Many state and area game laws prescribe a minimum caliber rifle for legally taking a moose. Long story short, you have to make sure you know and obey the laws in whatever area you will hunt. State wildlife authorities will gladly supply this information either free or for a nominal amount. Most are available online.
If you want to know what equipment it takes to hunt moose successfully, this is also a question that needs a narrower focus. Do you want to kill this moose with a modern rifle, a muzzleloading firearm, or with a bow and arrow? All are legal in many areas and have their own seasons and special regulations.
If you want to use a "modern" rifle, then the first subject most ask about is "What is the best rifle? What cartridge and rifle combination is the best? The answer is that it is a subjective matter, and every rifleman has a favorite rifle that to him is the "best" for the hunt at hand.
For a beginner, here are some guidelines for selecting a moose rifle:
1. As Robert Ruark wrote, use enough gun. Moose are really big critters, the largest of the deer family in North America. While many moose have been taken with the venerable .30-30 Winchester and .30-40 Krag (a once common Maine hunting rifle), a better choice among common hunting cartridges would be the classic .30-06 or the .308 Winchester. Either of these cartridges with an appropriate "premium" bullet/load will do the job quite well, assuming you do your job and place the bullet on target.
2. Don't over-gun yourself. While bigger may be better, the more powerful rifle cartridges make you pay a price in much heavier recoil. For a rifleman, especially a novice, heavy recoil makes it harder to learn to shoot accurately. Putting the bullet into the moose in the right area (shot placement) is much more important than the energy of the bullet.
3. The action or type of rifle should be whatever you like or are most comfortable with. If you have no experience with hunting rifles, find a local shooting range and visit. You will find a lot of people willing to give their opinions and most probably will be able to try firing various types of rifles. Shooters and hunters are generally glad to help those just getting started.
There is so much more that goes into any type of hunting, the full answer can only be, read some books about hunting in general, and your area (moose) in particular, and get involved with local hunters. They will be able to show you the way to a legal, successful, and hopefully happy hunt. May you have many meals of moose venison.
One final piece of advice. Ed Zern wrote many years ago that the best place to shoot a moose is not more than fifty yards from a pickup truck. He was right.