As with any game, when you first start out playing crucible, you will probably not be great. There are obvious exceptions, but those are the people who are going to be good at any shooter they drop into.
One of the things that makes Destiny a little different is that you dont immediately have access to all of the weapons, and the most powerful ones will be randomly picked up along the way. Just because you dont have a Thorn or The Last Word, doesnt mean you cant compete. It just means that you will need to find another way to win gun fights.
Step 1, Weapons: If you already have some of the top tier crucible exotics, then SWEET! If not, there are a number of decent replacements that are not too difficult to obtain one way or another.
Legendary Primaries are not all amazing. You can roll some of them to be serviceable, such as the Fulcrum handcannon that can be purchased from the Future War Cult vendor. It can be rolled into a mini Hawkmoon if you get luck in the chamber, final round, and something like smallbore.
In my opinion, some of the best non exotic primaries are in the Pulse Rifle category. The Messenger is top tier, and is two head burst kill and has ridiculous range. You can obtain this from Brother Vance in the Reef if he is selling it, or through the packages you get for winning games in Trials of Osiris. You can also get an Adept version of it in the chest after completing a flawless trials run.
One I have not obtained myself, but is apparently just as good and with the ability to be rerolled is the Hopscotch Pilgrim. This is a pulse rifle obtained through Dragon Strikes that has similar stats to The Messenger. It is apparently a pain to obtain, so be aware that you will probably be doing a lot of strikes to get it. If you are like me, that is not something I would particularly like to endure.
One thing about improving in crucible....dont let people get super salty and try to shit on you for using the overpowered weapons. You are there to dominate, and just because they think they are the White Knight Protector of Guardian Crucible Honor, you dont have to adhere to their dumb thinking. Here is a list of some of the top exotic primaries.
Thorn is an all around amazing weapon. It is a two headshot kill with the poison dot (damage over time). It is also a three body shot kill. It can be fired pretty quickly, and you can often beat out snipers over range if you can get them to miss their shots. Thorn is also the weapon that will cause the most salt for other guardians and you may receive a hate mail from time to time. The proper setup on Thorn is agressive ballistics and send it. Why dont you use the stability perk you ask? Well, first, send it increase the range by a ton. You will be getting cross map kills with it. Second, it also increases the hit box, and you will be hitting a lot more headshots with it. The recoil takes a little getting used to, but it is overall amazing.
The Last Word has one of the fastest kill times in the game. Part of it is that the fire rate is amazing. The other part is because the hip fire perk is bugged, and you often get the hipfire damage while aiming down sights. At medium range, there is nothing that can really beat it. It is also capable of defeating a shotgun user at close range if they are unable to get you with one shot. The proper setup on the last word is aggressive ballistics and perfect balance. Aggressive gives you the ability to get 111 head shot with the hipfire perk and bug. Perfect balance allows you to not shoot at the ceiling when you are firing.
Red Death is really the last of the top tier exotic primaries. If is a two burst headshot kill, and also heals you after every kill. This can be a direct counter to the Thorn dot bleeding you out. The only problem is that Red Death is a little bit worse than both of the handcannons, so you will probably have to get the first shot in to win most gun fights against TLW and Thorn.
Mida Multi Tool is a decent gun and can be fun to use, but I do not consider it on par with these other three. It is a great anti sniper weapon as it will throw off a sniper's aim. It takes four headshots to kill, which will get you killed a lot against the other weapons. It is mostly used in a more campy/support role.
Next article will be about secondary weapons.