The majority of my design "training" was done in a professional environment, using Illustrator and Photoshop. Such software has hierarchical layers/groups as well as support for keyboard input, which address your questions about performing tasks such as drawing circles and modifying designs.
Photoshop (raster-oriented graphics) is quite mature and impressive; there is unfortunately no OSS that can even approach its creative power, IMHO. Illustrator (vector-oriented graphics, which seems to be your interest) is nowhere near as solid as Photoshop... The best OSS alternative (for screen design, that I know of) is Xara Xtreme, which outdoes Illustrator in a number of ways. Unfortunately, core features such as layers/groups and keyboard input are not done well in Xara, and it is a long way away from being able to do print. Inkscape trails pretty far behind.
If you would like to take a scripting approach, how about trying JavaScript in a modern browser? In case it is better suited for your needs, you may also want to check out Asymptote and/or METAPOST.
A bit more advice: Technically-minded people can usually learn software applications by just playing around with it, but I highly recommend reading good books on the subject to really learn the software. The many design tutorials online can also be quite useful.
http://www.xara.com http://www.xaraxtreme.org/ http://asymptote.sourceforge.net/