I will recommend the combo in a way that reflects the future when patches fix some of the missing parts like sawmills. For age 1, the choice is really up to what you need in a game. Another aspect to consider is when it comes to the fourth age and you can use the princess guard card. For me, portugal and spain make more sense because they provide better ultimate units in the fourth age, the batidor and the atirador which are flexible units as far as uses is concerned. Age 2 should go to either dutch or swedes unless you want to be agressive then use the other two options. Age 3 should more than likely be maltese unless you want to build artillery upon age up then use the greek princess so you don't need as many mills or plantations. The final age is up for discussion. Polish and Serbs are the most popular options I see in games, yet the others could prove useful as well.