I am not a fan of starting with text based games ... they deal with weird comparisons and you are likely to end up with weird switch statements or nested ifs.
IMO the better idea is doing some of the Google Code Jam challenges. You are forced to learn to think like a programmer and you will be able to apply that way of thinking to making games later.
To decide if ISO is too complex to implement or not you can look at the tutorials that are listed there:
Converting Cartesian coords to ISO coords and figuring out which ISO tile the mouse is hovering over, those are not quite trivial ... but doable.