There's no actual "right" answer to your question. Setting aside individual abilities of kids... SCHOOLS all approach math differently. In my son's preschool, the kids were doing sing and double digit +-x/ by age 4. In the elementary school he would have gone to (we homeschool now, as well) they didn't even start addition and subtraction until grade 3.
My son is a numbers guy (doing algebra this year at 8) but he does NOT have math facts memorized. Instead... in his preschool, they used montessori math... which visualizes everything, so at home we've continued the trend, although we also use Singapore (starting this year) & Cluefinders. Even now, in algebra (borenson) he doesn't memorize formulas... he learns the concepts behind why to use formulas. (AKA look at the equation, okay, what's it asking and why? How would we do that?) My numbers guy uncle (astrophysics) still taps his fingers (counting them) as he's working out problems. Memorization of facts isn't something that everyone GETS. Some people are just very visual or kinesthetic in their learning/recall... while others are auditory/rote.
I NEVER thought I was a math person (science, history, art... yeah... math? Hail no!) until I started HS'ing my son. I've completely "relearned" math teaching him... and low and behold... it MAKES SENSE NOW. Go figure. Just an entirely different approach than the way I was taught.
For preschool - algebra check out : http://www.freemontessori.org/?page_id=9 be warned, each album (free) is a couple hundred pages long.
Ditto singapore (not free) is pretty phenomenal in a very different way than most American maths are taught http://www.singaporemath.com/Homeschool_s/60.htm
We also do a lot of online math games (the ClueFinders I mentioned before). My son is a very visual & kinesthetic learner and the interactive games really help him a lot without it looking like "work". It is NOT a teaching program. Definitely supplementary.
Due my getting a little burned out this year, we also started Time for Learning. My son hates their math program (so we don't use it at all), but it comes bundled with the English program we do use. At $20 a month it's a lot more affordable than many options out there (and a lot more affordable than it used to be). It actually IS a teaching program, so it's something to check out. They have a 2 week free trial, which is nice, since learning styles differ so much.