Hi Matt.
It's not the gear.
I am going to assume you want to really blur the background, as you will struggle to get massive depth of field with a 200 lens.
You have to think about focal length: the longer the lens the more shallow the depth of field no matter at f2.8 or f22.
You also need to think about perspective, i.e. the distance between the camera & the subject and then the subject and the back ground.
The closer the subject to the camera, the more out of focus the background will be.
Most folk assume the ratio that the distance between the subject and the background should be at least double the distance between the subject and the camera.
As a guide, set your lens to f2.8. Set your focal length to 100mm.
Place your subject so they are against a distant expansive background (cityscape, landscape) zoom with your feet.
With the camera in portrait orientation move back from the subject until they are shoulder width filling the frame with the eyeline 2/3 up the frame.
Take your shot.
You should get sharp subject and soft background.
You can accentuate this by zooming to 200mm and moving back further to keep the composition, although this will 'flatten' your subject.
With the best will in the world mate, you have the gear, you need a class to get the skill. No offence.
