As OpenGL version a suggest 3.3+ because almoste all modern graphic card support it and is very similar to OpenGL 4.0.
As GUI library you can use the Qt library.
As math library you can use Eigen (very fast with extensive use of Expression Template and SIMD istruction (SSE, AVX, Neon)).
But you have to learn very well GLSL language. OpenGL is a C API and is not easy to write OOP code. Take a look to (http://oglplus.org/)
GL 3.0+ is still not very widely supported. If you are targeting a casual market, you may want to stick with 2.0 as your target. In this thread it was listed that as few as 51% of Minecraft users supports GL 3.0+. It really comes down to what you need; GL 2 is a fine target for most purposes and can be used in almost the same way as the 3+ programmable pipeline (shaders, custom built-ins, etc). Many drivers will support geometry shaders, FBOs, float textures, etc. through extensions. For example, 93% of drivers support FBO EXT, and it's pretty much a staple in any driver in the last several years.
GL 2.0 and GLSL < 150 is also more compatible with OpenGL ES, so it will prepare you for iOS/Android/WebGL graphics programming.