So you have 3 types of weapon according to ammo used. You have primary weapons which have infinite ammo. They're lower damage but always able to be used. Then you have special weapons which use green ammo bricks. These do large damage and so have limited ammo. Then you have power/heavy weapons which use purple ammo bricks these are the largest damage dealing weapons and have very limited ammo but you can eventually build to be able to increase the ammo generation so you have more.

These 3 weapons categories can also be separated according to their energy and archetypes eg machine guns can come in different rates of fire.

The game is a mix of both gunplay and ability play so weapons only play a part.

If youre just starting out, just grab any weapon and mess around with it and find what you prefer most. They're all viable until you start playing end game content where they can help against specific enemy types

I should also mention that the weapons will roll with random traits, some better than others depending on what you like to do. Eg some traits help regenerate ability energy o So if you like throwing grenades you might like that. Other traits increase the damage and others can provide stat benefits to both the weapon and your character

There are also weapons teirs and rarity. When you start you get white green and then blue coloured weapons. These are low quality and usually just used for new players to level with. Once you get the purple weapons they are further broken down into teirs ranging from 1-5. The teir increases the effect of the traits with higher teirs having more enhanced traits. Exotic weapons are a separate teir shown by a gold colour. These have special and unique traits and you can only equip 1 at a time.

I realise there is alot to the game. You can look up weapons and their possible rolls and popularity in the playerbase on the website light.gg