Checkmate Research Development Numbers Guide by sodomizer
Earning development is fairly easy but this will break down the increases that you receive for T1 units.
1 infantry = .25 development
1 tank= .25
1 artillery= .25
1 transport =.25
1 truck= 1
1 Heavy Infantry =.74
these are the numbers ive come up with in testing. So the fastest way to build dev early on is trucks. the trucks will serve a use later to move your gold around to other cities. Early on you will need the Dev for development packs. also for mission rewards. hope this helps.
i will update this info as more becomes available.