When you're just starting out, C, C# and C++ might be a bit complex to start with. If you're serious about game development, you will probably need to learn C++ eventually, but if you just want to quickly get some things done, you're already on the right track with lua.
Javascript is another language which is very similar to lua in many ways (and very different in others). One advantage of javascript is that everyone in the world has javascript installed on their computers. Another advantage is that it's very easy to learn. There are disadvantages too, but they are not nearly as bad as most "serious" programmers think. Javascript gets an undeserved bad rap.
Here is a very good tutorial for learning javascript:
http://eloquentjavascript.net/
It does not cover games programming, unfortunately- But it does cover concepts that are relevant to both games programming and application programming.
Here is a tutorial for javcascript that does cover games programming:
http://billmill.org/static/canvastutorial/index.html
you will need a web browser in order to follow that tutorial. This does not include internet explorer, so you will probably want to use safari, firefox, or opera.
Once you are comfortable making games in an easy language like javascript or lua, then it will not be quite so hard to learn to make games in a hard language like C or C++.
On the other hand, you might be happy just making games in the easy language, and that's okay, there's no rules that say you have to learn C or C++ to make good games. Good games come from good ideas, not difficult programming.