There are MANY (soooooooo many) math curricula out there. There is no 'right one.' But you will find some work better for you and your child than others.
I recommend you try ONE math curriculum your first year, maybe a second one if the first one you try really doesn't work. I am ALL for trying new things - but decision paralysis sets in pretty quickly with too many options.
It IS technically feasible to find materials online at no cost to do homeschool math: but the amount of time that would take, plus if you are printing items: just bite the bullet and buy a curriculum. You can find used textbooks and teaching guides on ebay and homeschool facebook groups, especially for older grades.
A few ideas:
Get connected to a local homeschool group or Facebook group. Talking with parents who have USED different math curricula is so valuable.
Search ebay for "Math + grade level" - this will give you some inexpensive options to try.
My personal preference is the Saxon math series, in my experience it leads to true mastery of the material. But this is MY and SOME of my students' preference: it will not be the perfect fit for everyone.
Some cautionary notes:
Please, please, please, use a pencil and paper approach. This is CRITICALLY important for the youngest learners, but holds through all levels of math (including and beyond Calculus in high school and college). The act of ACTUALLY WRITING BY HAND is so incredibly important to learning, very much to include math!!!! If you do decide to use an online/digital curriculum, writing problems on REAL PAPER is critical (1).
Bring the math OUT of the workbook or textbook whenever possible, most especially in the youngest years. Encourage students to tell their own stories about addition or patterns or whatever it is they are learning in a designed curriculum. This is just as, IF NOT MORE, important than the 'book work' they do (especially at the youngest ages). It HAS TO relate to themselves and their life to have real meaning. Favor projects where they can show the concepts over more practice problems in a workbook. PLEASE.
This is a fairly specific complaint, but the IXL approach is, well, not great in my opinion. In my experience students universally hate it as it punishes wrong answers more that it rewards right answers...but that isn't the worst part: the worst part is that it is punishing wrong answers and rewarding right answers at all! It makes kids afraid to make a mistake which is the worst possible outcome for kids. Mistakes are an INTEGRAL part of learning. IXL is aligned to national and state standards (which SOUNDS like it should be good, and huge numbers of public school teachers use IXL as extra practice for students now). What this standards alignment actually does (in my opinion) is create an incredibly LONG list of 'skills' to be learned at each grade level, but with no need for deep understanding. (But it is a system that where student time and progress is easily tracked, which is why it is popular. But the system is fundamentally flawed if mastery of mathematics concepts is what you want.) However, if you want to use it as extra practice or for letting your child try questions in a different format: go for it. Just don't make IXL your MAIN math curriculum please.