Bleeding gums are often a sign of inflammation, which needs to be brought under control before orthodontic treatment begins. The cause may be a build-up of tartar or difficulty cleaning the teeth, especially if they are severely crowded.
Aligning the teeth orthodontically makes oral hygiene easier and, in the long term, can improve the health of your gums, because it will be easier for you to clean between your teeth.
This answer is for general information. Your own case needs an examination by an orthodontist.