I would not suggest a private tutor with a score of 650. How can someone teach if they are unable to do well themselves? For instance,
Manhattan GMAT doesn't hire any tutor that has less than 99% (aka 750+). They do this for a reason. Obviously you will pay more for more highly educated and experienced tutors. But I would definitely suggest going for someone that has a reputation. There are many great comapanies on our website that would be happy to help!
BUt more importantly, you need to figure out why you're not having the success you want. Maybe you need to try some new materials? Maybe going back to foundations so you can build up to more advanced topics. Maybe you just need to spend more time, or quality studying. It's hard to say... only YOU will know the answer.
Good luck! We look forward to supporting you in your journey!