Welcome to the board.
You don't need all the fancy rulers. You need to practice cutting accurately. That is one of the first rules of quilting. You may think 1/8" isn't much but add up 8 blocks and you are off by one whole inch which is a lot. Practice cutting on old sheets or tablecloths from the good will shop. Your straight ruler will do all the things the fancy ones can do. Same as Deborahlees I mainly only use two rulers 6 X 24" and my 8 1/2" square.
Come back anytime and remember we are all here to help and be helped and there is no such thing as a dumb question. Happy quilting.
PS If you only want a square to square up blocks go to a plastic specialist and ask them to make you an accurate square in the size you want. Much cheaper.