I heard that a lot of successful player started with OoD.
All depends on what you want to achieve and how you want to spend your real estate and produced fp and then split it into milestones to achieve:
-You want to play it the way Inno planned it? then age up and wait patiently to get BP + goods.
OR
-You want to have the basic fighting power: Trio
-You want to have troops harvest Traz
-You want to have goods income and finish GE4 with a mix of fight/negociations CF
-You want to bank fp Arc
-You want to build a diamond farm? no GB gives diamond.
Level them at a satisfactory level and then rince and repeat... All that also depends on the time you can allocate to the game. I got two cities, a city where I just enjoy with a mix of fp + fighting and then another one where I purely focus on fighting.
Just plan, play and enjoy.