I found a free (and ad free) mobile game that's a lot of fun. It's called Polytopia and it's a civ-style game where you build cities, harvest resources, build infrastructure and wage war on you neighbors. There's not really any diplomacy that I've seen yet but overall it's a solid game. No ads, the only in-app purchases are additional civs at $0.99 each. The 4 base civs are decent and you can unlock a further 8.
The time line is not broken up into formal technology ages but the game ends in the medieval era. Basically, once knights show up the game will end pretty quick. They move fast, have powerful attacks and can attack multiple times per turn so they break through the slogfest that the midgame becomes with archers, swordsmen and horsemen.
The game has two modes - timed play and free play. Both are fun as the timed play forces you to focus on objectives while free play is more freewheeling. You can only win through conquest that I've seen but you spend a lot of time and effort on research and tile development. The one free play game I tried really dragged out once all of the other empires were consolidated under myself and one other AI. For 30 turns or so we painfully, slowly murdered each other with ranged units as we vainly threw our melee units at city walls and entrenched positions. The turning point was when I got knights - I didn't know they were so powerful so they were literally the last technology I researched.
Once I got knights I swept the map in about 5 turns. It's a lot of fun.