if it was me, and it was going to be my one and only, it would be shiny black poro with phw.
shiny so it can dress up and down. black because i think i would tire of graphite over many years with only one croc option and it is dark grey. poro because i like scale size variance across the body of the bag as opposed to more uniform square nilo. phw because while ghw is a tad more trendy right now, phw will stand the test of time.
in terms of gator and nilo, both are less expensive than poro so that could be a factor as well.
keep in mind this is super subjective and you should choose what you love most, as it is a big investment!! just because many people may say black, if ebene or graphite makes your heart sing then that is the right choice. can't wait to hear what you choose!
I totally agree with LamborghiniGirl!
At the end of the day, black in either matte or shiny will look stunning. I think you should really do your research, and speak to your SA as much as you can/ see swatches if possible, to see which type of skin jumps out at you.
As for which colour to choose - only you can make this decision. Black is a colour that you will be able to wear with any outfit. However, if you love bright colours, and already wear alot of dark clothing (like me ), then perhaps you should consider a brighter coloured bag? Or if you have a favourite colour that you love to wear, maybe even go with that...?