As for the proper type of collar/harness, get something like a gentle leader that will loop around her neck and around her face as well. She won't pull because the loop on her face will either become uncomfortable or redirect her gaze when she tries. If you are worried she may break them you can put a collar on as well and attach it to a longer leash tied to you somehow and have one leash attached to her gentle leader. Do not go with a harness. A harness is made for dogs to pull on and will make it harder for her to tell when she's putting pressure on you.

Have you done any impulse control exercises? That may be able to help.

Is the dog receiving plenty of mental stimulus? Dogs who are under stimulated often become way over excited by stimulating things they see on walks because that's the main stimulus they have access to. Around the house things like food puzzles, kongs, training, and food games will help keep your dog occupied and stimulated.

Do you allow the dog to eliminate on walks? He should either go before or after to help reduce distractions. I like doing before because then my dog seems less distracted during the walk but some go after as a reward for behaving on the walk. I'm skeptical of this because I don't see how the dog will link the behavior on the walk the last 30 minutes to being allowed to pee in the same spot he always does.

Does the dog have another source of exercise during the day? Walking alone may not be enough. German Shepherds are high energy dogs that will require 1-2 hours of hard exercise to tire. Since you have a mix you'll have to judge whether she receives enough exercise or not based on her behavior. Dogs who behave neurotic and clingy and are always excited are generally under stimulated or under exercised.

How do you respond when she pulls? You should always immediately stop your walk until she returns to your side or begin walking the exact opposite direction so that she is forced to follow you. Whichever you do you will need to do it every time to build consistency.

I'll include a link to Kikopup's loose leash training video because she makes some excellent points as well: