Another option is to create caret-style (>) arrows by typing a caret or, if going with Jonathan’s suggestion, by using a stroke on the rotated box and no fill.
Note that you can use symbol webfonts as well.
My preference is to use Photoshop to create the arrows and drop shadows, and outputting them as PNGs. Monochromic arrows don’t work well on backgrounds that vary in tone and the drop shadow helps the arrows stand out regardless of background.
As for bitmap editing apps you might consider Affinity Photo or Affinity Design. They are both very powerful and very inexpensive ($49 from the Mac App store).