At the very most one or two shades darker than your skin is the darkest you should go but also remember to lean in towards hues that have the appropriate undertone to them.
Best contour for light olive skin.
If you want to add shimmer try using a highlighter as well as bronzing.
The most flattering type of bronzer for a medium or olive skin tone is a matte bronzer as this will enhance your skin s natural warmth.
From subtle nudes and pinks to bright oranges and purples it all depends on how comfortable you are and how far you are willing to take it with your experimenting.
The best bet is to choose a contour shade a bit darker than your foundation and a shade that is similar to how you think shadow on your face would appear.