How can i modify gtm pools ratio value

Here is the cloud docs information on this with the API endpoint and options: https://clouddocs.f5.com/api/icontrol-rest/APIRef_tm_gtm_pool_a.html. You may have to tinker with this using a test pool setup within the GTM module. I would do a GET request to see how the JSON looks, and then try to modify (only the ratios) via a PATCH request.

You can also use Ansible, and the documentation here is a bit better: https://clouddocs.f5.com/products/orchestration/ansible/devel/modules/bigip_gtm_pool_member_module.html.