Contrary to what has been stated in this topic already, you can do two squares of the same planet but there is a rule: they must be of different type. For example, you can do spiritual Sun square and a material Sun square at the same time. There have been countless questions in the past and many people have experimented and found out they don't interfere with one another.
You can also do two squares of different planets at the same time.
How much spacing you use for them is extremely individual as there is no "one size fits all" when it comes to spirituality.