RESEARCH - The very first thing I would suggest is to research your subject areas and standards. Look on your school website or Google your grade and state standards. Make sure anything you purchase from TPT matches these standards. Don't spend money on it if it doesn't match.
PRIORITIZE - You will not be able to accomplish everything you want to accomplish. Make a list with 3 categories (see below). Spend time each day knocking things off the first category. If you have extra time, move to the next. But only if you mentally can handle it. Never use one large to-do list. It makes you go crazy!
Must do now - things you have to do get done in order for your classroom to run
Must do later - things that you have to get done, but you can currently function without it.
In the future - things you really want to accomplish, but aren't an immediate need.
ORGANIZE - I am a firm believer in "if your space isn't organized, your mind won't be either." This goes for your classroom and your lessons. (see my other organizing tips below). Everything in your classroom should be organized by category. All of your teacher items shouldn't be mixed in with student items. Label everything. For your lesson plans, decide if you will do paper or digital. I love digital because they can be accessed from anywhere. If I'm waiting at an appointment, I can access them from my phone or iPad. It saves time in the long run.
MANAGEMENT - First year teachers often struggle with classroom management. Let's be honest, what they teach us in school is not what we see in the real world. Make sure to teach Routines, Procedures, and Expectations for the first full week. Revisit after any long breaks. Find a classroom management system that you think will work for you. I LOVE Class Dojo because I can access it from my phone, iPad, or computer. The students have a great visual and I can include parents if needed. Having parents view their child's information helps cut down on parent phone calls which can also take up a lot of time.
ASK FOR HELP - I was lucky enough to work with some amazing teachers. They were always willing to point me in the right direction. Some even shared their materials (not all will do this and that is okay). I've also worked with some who didn't want to speak to me, but those were few and far between. Those that did help, gave me inside information that I wouldn't have learned from my own research. Don't be afraid to ask. However, try to steer clear of asking your Principal (or leader) some view it as being weak or inexperienced (which is terrible, I know first hand).