A great base is the "what your fifth grades needs to know" books (one for each grade).
You can't go wrong with just the basics. Hake for grammar and writing would more than cover you for grammar, vocabulary, composition (in one swoop), if you're sure she's strong in all pre algebra skills (firm in decimals, fractions, ratios/proportions, percents, exponents, integers), you can then find a very cheap Jacob's algebra used on Amazon for very little; if you need pre-algebra, College of the Redwoods is FREE online. For science you could buy a science encyclopedia and have her outline from it ($20 tops) and supplement with library literature. For history you can do something similar - buy a history encyclopedia and outline from it.
Right now our budget is extremely limited because hours have been cut. Hoping that will change soon. I typically don't use a standard curriculum. I find things on the internet and work with that. It has worked very well so far with 5th grade, her math is up at Algebra level and her reading is improving, though she was never behind.
I wish there was a better guideline to go by what they should know by this age. I have gone to some of the websites that show the core standards, but they just really don't help me. I know that most of what I am teaching she already knows and it is just repetition, but I feel there could be more.
Sometimes I feel more lost than others and maybe today is one of those days. Plus looking into the next year just scares me knowing that she will be middle school (she is my baby).
For middle school start with your basic subjects: math, language arts (composition, language arts, grammar), literature, history/geography, and science. Then you add in your "extras": art, music, foreign language, etc. The extras are up to you.
Are you lost on curriculum providers? What's your budget and faith preference (secular, protestant, catholic)?
I will begin ordering curriculums when we get our taxes back. I have already been plaaning on what we are gonna use though. I also do a pot of shopping on ebay. If I had money now, I would have already ordered several things. I just hope IT will be able to find good prices when I actually have the money to order stuff.