I like the Olfa cutting mats and rotary cutters. I LOVE my 6 x 24 O'lipfa ruler (I think that is how it is spelled). It has a lip on it so it is easy to line up and make sure the ruler is square with the mat before you cut. As budget allows, it is nice to have cutters in different sizes - I use my 45mm most, but also use a 60mm and a 28mm often. If I could only buy one cutter, I would go with the 45mm.
Good luck and welcome to the world of quilting! You are going to love it!