Congrats on the new job!
I also teach math, high school Geometry and Algebra 2.
This is my 11th year of teaching, the first few years are more challenging. You are sometimes only a day or two ahead of the students in lesson planning, plus you are trying to figure out classroom management, the school climate, etc. Are you familiar with the district? Having a good mentor is huge the first few years. Having someone that you can talk through issues with classroom management (everyone has them especially in the beginning when students are testing you to see what they can get away with). I'm pretty firm with my students, and have high expectations for them. I know I'm not their "favorite" teacher because I don't let them goof off and slack. But, I'm totally fine with that. I'm their teacher, not their friend, and it's my job to help them learn the content in the class. But, I also have a lot of catch falls to help students if they are struggling. My students know what I expect of them, I have learning goals for each section. I have my students refer to where they are on those goals at different points during the chapter, if they aren't at a "passing" point for the goals then we go through them again so they can be successful. If possible, make the quizzes and tests before you teach that chapter to the students (or if you don't make your own quizzes and tests, some districts don't allow this) make sure you review those before you teach that chapter. That way you can help the students with the points of the chapter that are most important (should be the same as what's on the quiz or test).
Wow, sorry for the novel. I'm sure you will do great. Teaching is a hard job but SOOOO worth it. I love watching students go from completely lost to that ah ha moment.