A top-ranked Clash player actually went out and made his own similar game, Samurai Siege, and Gameloft has a Rome-themed knock-off called Total Conquest. Candy Crush Saga and Simpson Tapped Out are both solid options. If timers have got you down, play a few other games and cycle through them. On the flip side, you'll have a hard time getting through the competitive end-game content without spending some cash. When you do have enough gems, think long and hard about what's important to you in the game, since if you want to get through this without paying a dime, it'll take awhile before you make another major purchase. Typically, buying resources outright with gems is a poor use of resources you're better off boosting your own production buildings. After that, there's a wide range of discretion on gem spending.
Above all else, gems should be spent on builders huts. Make a point to complete achievements and clear natural obstacles to build your gem count.
Save them for something important that you get to keep. Don't cave and spend your precious gems on speeding up production. Just about everything is on some kind of timer, and as you progress, those timers get longer. The biggest caveat with any casual free-to-play game is the premium currency system.
