First, I would think about what style of homeschooler you are and what would suit the learning style of your child - classical, workbook/textbook based, literature based, unschooling, and so forth. Within each type of schooling you can find many different cirriculums to choose from - these will help you stay on track with the material to cover and staying "at grade level". You can use different cirriculms for each subject, or use one program across the board. If one turns out to be a poor fit for the teaching/learning styles in your home, you change.
After doing some research, we decided we love both literature based and classical perspectives, and we are going to merge both styles inour homeschool. We use Sonlight as our curriculm for history/geography/social studies, a combination of sonlight LA and my own materials for LA (language arts/english), saxon math, apologia science, a hodge-podge for special subjects like music/art/gym, and we plan on starting spanish in middle school with rosetta stone.
Basically, start reviewing different cirriculums and get familiar with what you state requires - each state has different accountability laws and subjects required and so forth. Using a pre-estabilished curriculum can make accountability to the state easier. But you need to find materials YOU are comfortable with using and that will differ from family to family.
We started homeschooling with the pre-K level. I felt like this gave me time to try curriculums and get a taste of homeschooling with no pressure to report to the state and if it went poorly, I could always go back to the institutional learning with no harm done because, well, it was only pre-k. But it went better than expected, and my kids love learning together. What started as a "maybe we can do this until 2nd or 3rd grade" (between me and my husband) has become "why would we ever bother with the drama of institutional learning when this is so easy to taylor to our children's needs and our family's needs. Lets do this through 12th!"
So point being, there is a learning curve, and I personally felt more comfortable getting my feet wet with a preschooler than at a more serious level. It worked for me. Do what works for you - that is the joy of home education - it can be exactly what you want it to be!
Good luck Mama. PM me if you have any questions!