I just newly switched to theoretical chemistry from experimental kinetics. Presently I am interested to find out the band gaps of some simple metal complexes or organic complexes. How can I start? I have a very small experience on ab-initio methodology. Especially I used DFT calculation for optimization of structures, IRC calculation and so on for mechanistic interpretations. I used gaussian09 in Linux and Gaussview for previewing. Can anybody suggest me shortly as a whole for the process of my interest or help me giving some useful links for beginning?