Hi Cindy,
Apologia is a great choice to get you started in science. You only buy one book, on whichever of the subjects you would like to cover this year. We have especially enjoyed the Astronomy and Anatomy books. Generally you read it with the kids and do the easy experiment at the end of each unit with them.
Some people also buy the notebooks Apologia sells to accompany thier series, but I haven’t found it to be necessary. Most of the pages are available online if you would like to supplement with them occasionally.
Welcome to homeschooling and be sure to download the free ebooks at the top of the SCM home page. There is a LOT of valuable info there :). Blessings!