<p>Doing well in the AMC-series definitely will only help your application. However, don’t do these contests JUST to write it down as an achievement. The purpose of these contests is to encourage interest in challengeing problem solving, so actual scores on the competitions matter less than learning and enhancing your creativity in math.</p>
<p>And yes, contest math (the good contests) just test your creative thinking. A lot of the problems can be solved with no more than Geometry, though you do need to work hard to find the right approaches.</p>