Installing Firebird Ruby driver on Windows 10 x64

Install firebird 2.5.4 x64 with fbclient copy to system dir (checked).
Install rubyinstaller 2.x x64
Download Devkit for ruby 2.x (x64 – 64bits only)
unzip it in C:\rubydevkit
open cmd.exe in start->run
cd rubydevkit
run ruby dk.rb init and ruby dk.rb install to bind it to ruby installations in your path.

Then gem install fb will go without issues after compilation.
After that you can install rails 4.2.x and ActiveRecord Firebird Adapter.