i am a bad one t ask because i went for a whole year and got up to a gram a day without any of the other stuff, not even selenium. it was dr olree who convinced me to take selenium.
"the body starts making cancer when it runs out of selenium"
start training your instinct and trust yourself. more of any of those things wont hurt. the max on selenium is 400-800mcg and boron 9-15mg. if you eat too much salt you just pee it out or get the runs. same with C.