We like Singapore. Dimensions is the newest version, but we like Primary Mathematics Standards Edition with the Home Instructors guide. It is getting hard to find right now because of current events though.
I took two free classes from Well Trained Mind taught by Kate Snow on how to teach it. Not only do I understand it, I see the value in the methods.
Beast Academy is good for gifted kids if they would rather do fewer, harder problems, so I’ve heard.
Rightstart is more teacher guided and less worksheets, but I didn’t understand the concepts as well, so it was a struggle for me to teach.
Show your child samples and see what he likes, after you have figured out what works for you.