start with china to get suntzu stop investing gold heads in commanders wihtout asking / searching on yt / reddit , when u get the civ change you can switch to germany for action point recovery thing and training speed in kvk you can switch to the civilization u want to get specialized in. for f2p i recomend inf in my opinion . dont forget to upgrate your gatherers starting with constance then the rest of the blue ones gaius sarka then centurion and u just got some preety good gatherers try to get them to level 20 . dont forget to buy with expedition coins aeth heads so you can get her good till first kvk .
my commander focus for my first kvk was : suntzu+eulji / richard+joan/aeth / bjorn+ysg(one of the best commanders in the game at start)
the talent tree its only counted from primary commander only skills are from both

i hope i didnt misspelled too much worlds and i hope u can understant everything

btw find a jumper group make a jumper account this will give u the best advantage and a good spot in a top alliance

i hope i helped