Can the forum members help me with which flash to use , i am nikon user . I find every hot shoe in a sony shop has different pin configurations & the guys here in Dubai don't have a clue on sony systems 

You need a flash which has the Sony MI (multi-interface)foot.  These are made (obviously) by Sony and also Metz and some other brands.  Be careful - just because it says it is for Sony does not mean it has the right foot, as most Sony cameras have used a different shoe known as iISO   Details at http://www.mhohner.de/sony-minolta/flashcomp_techref.php.

 

The foot should look like this http://www.pbase.com/gregglee/image/150669591.  It is actually a picture of an adapter (ADP-MAA) which takes the previous design of foot, but if you are shopping for a new flash, you may as well get one with the correct foot.

Sony flashes with the MI foot have numbers ending in M but not AM (AM means the iISO foot).  There is no easy way with the other manufacturers afaik.

I have the Metz Mecablitz 52 AF-1 (52316S) and it's great with the A7ii.

I use a Sony HVL-F43M and a Sony HVL-F20M. Both will work on the MI hotshoe. The F20M is too small really but works great as a remote trigger for the bigger flash for off camera.

I have a Nissin i40 and it's a great compact flash IMO. If you go on B&H Photo just narrow your search to Sony MIS Flashes and you will see your 10-15 current options available from Sony, Metz, Nissin, or Phottix.

+1 on the Nissin i40; I use it on my A6000. Very nice for the amateur stuff I do; I don't use fancy lighting (yet ).