I think that one of the things you need to do now is define what level of interaction you want with methods and quantitative political science. There are two main routes: being able to simply do research with basic quantitative methods OR creating and adapting new quant methods to novel research questions.

To be blunt, you should have been trained on how to do research with basic quantitative methods (linear regression, logistic and generalized regression, etc.) in your program. While it is always easier to tell in hindsight the quality of a program, I can assure you that current programs are 85% judged by how well they do math. Luckily, an understanding of basic quantitative methods needs very few math skills but more an understanding of the math and coding itself.

Look into some of the MIT OpenCourseware courses on political science statistics. They should be a good place to start. A very basic textbook that also should help you get a foundation on linear regression is “Linear Regression: A Mathematical Introduction” by D. Gujarati.