Radical suggestion: Practice moving around your house with a gun-like object (I used a drill so I didn't have to worry about pointing a gun at any family member or neighbors) while keeping it aimed at whatever direction you designate as "the berm." Lots of people coming into gun games DQ themselves by sweeping their body parts or breaking the 180 because they point the gun somewhere inappropriate during movement. In gun games, pointing the gun up or down are both flirting with a DQ and a big waste of time.... you need to learn to tie an imaginary string between your muzzle and the berm. Practice moving left, right, forwards, backwards... practice trailing the "gun" behind you with a left pivot (right arm stretched behind you) and with a right pivot (right arm crossed over your chest), and getting out of those trailing positions by turning back into the gun (not spinning it through 270 degrees, even if that's more natural).
Sounds like you already know how to shoot. And you may already have movement-with-gun stuff ingrained that you will need to overwrite, hard and mercilessly, to avoid DQs on stages with complicated movement. Maybe focus on that, and then get to a match soon! Plenty of time to get good later. First, make sure you can stay in the game!