I am in grad school but did not work in 2018 and did not pay student loans from undergrad. Can I get/claim a tax credit for being in school?

If you have no income and no tax due in 2018, there is no need to need education credits as they are non-refundable.

Only the American Opportunity tax credit has a refundable portion but you are not eligible as you are in graduate school and have completed at least 4 years of post secondary education.

Also, if you are claimed as a dependent by your dependent, you cannot claim any education credits.

anything else I can do that would get me some money back?

No.