You can gain more perks in Call of Duty: Ghosts by choosing not to use some slots. Each of the primary weapon, secondary weapon, lethal and tactical slots gets you one extra perk point. Note that not choosing a point streak will not gain you extra perk slots.
The Ameli Light Machine Gun has the second highest accuracy with the highest damage of all the light machine guns. It has fairly high range but a low fire rate and mobility.
The Ameli is best at medium range but also works well at long range and short range if you are prepared for enemies.
The Tac 12 is a pump action shotgun with the most range but lowest fire rate of the shotguns. When you aim down the sights of the Tac 12 your spread is reduced. With the Tac 12 it is possible to complete objectives that only require close range combat. Avoid open areas when you move around the map so that you don’t encounter enemies you can’t shoot.
The MTS-255 Shotgun is a double action shotgun which essentially lets you fire semi automatically. It has the highest fire rate but is average otherwise. The main problem is the small magazine size, you only get 5 slugs between reloads. Move around the map so that you stay in close quarters and always fire from the hip.