What kind of doctor is best if i plan on applying for disability?

Based on problem: Your question begs the question - do you want to try to get help for your medical issue or are you just trying to get disability? If you want help for your issue it is important to talk about what the disability is - one problem is that if you want disability they are going to look and see if you have gotten medical treatment to try and get better. You also need good documentation.

Depends: Disability at your age is rare. If you had a disabling condition as a baby or child, medical records from pediatrics and neurology is necessary. Psychiatric disability requires psychiatry and neuropsychology. Physical impairments require functional findings, usually with medical, physical medicine and physical therapy reports. The condition must last >12 months, and be completely treated.