How to take pictures with blurry backgrounds on nikon d90? - 1

I use nikon D90 with the kit lens
and when I use manual mode and set the F stop to 3.5 (the lowest it can go) it doesn't make a difference to the focus of the background, as to when the F stop is a higher number.

the only time when the background is out of focus to the extent i want it to be is when i zoom in all the way but sometimes i want the out-of focus background without doing that.

what settings do i need to use so the background is more out of focus, or do i simply need to buy a 50mm lens?

You have already found that a wide-angle setting (around 18mm) does not help to get blurry backgrounds, you basically only get blurry backgrounds at full aperture (f3.5 in your case) and at a zoomed-in lens setting. Buying a 50mm will not help, since it is just about equivalent to your lens at 55mm, but indeed it has a larger max aperture so would be even more blurry at F1.8, but would distinctly not give a 'non-zoomed-in' style of pic.

It's a basic law of optics that wide-angles (say your lens at 18mm) do not allow a blurry background. See if you can borrow a 50mm to try.