Thank you guys, I appreciate all the feedback and suggestions + personal experience.
To me D90 worked great except few things:
a) low light - i lost ability to take pictures when my friend with D800 kept shooting.
b) focus - although this one is a bit mixed because I was told by guys here that my combo of D90 + 50mm 1.4G Nikon lens is not ideal and suffers from blurred images issues, but still - AF on D90 is good (except with the 50mm lens as that ruined my experience when I was at a photography workshop and almost half images were blurred despite me having the correct focusing point etc.) but I feel that the ability of D750 to recognise face and focus on eyes will be a major game changer for me.
I'm thinking of finally testing properly home "studio" portrait shooting so was hoping to get some suggestion for equipment.
I think I need the umbrella (softbox they call them I guess) + stand for it + trigger cable (I think its cheap compared to radio ones and more solid, right?).
I have SB700 already as I used that for a wedding few years back.
Eventually I'm waiting out to see what the Sigma art 24-70 turns out to be as I might consider getting it.
Also, should I keep the 50mm 1.4 G lens or get the 1.8 as people say its much better and sharper?
Or maybe 85mm 1.8G for portrait?
For now I think I'll play with the 50mm but wonder what are the options etc.
Thank you and see you guys soon around here
Go to http://strobist.blogspot.co.uk/ for a great set of tutorials about setting up your home studio.
The softbox is different to the umbrella but they do similar things in that they help diffuse harsh light from the flash. They do it to different effects though.