I have been playing for quite a while and was able to get most of my endgame stuff as a f2p player. I ended up spending money only because I wanted to and to help support the game. The important thing is that I never felt I had too. Edit:2022/ this game has become a pay to win mess. The drop rates now feel so low and insignificant that you will never get the units you want unless you pay an absurd amount of money or you are very lucky.