First off, you will want to have either offence or defence, not both, unless you have just your first village. Offensive units are units with high Attack stats. Click the images of a unit to view its stats.
Offensive: axe, light cavalry, mounted cavalry, heavy cavalry*, rams, catapults
Defensive: spearman, swordsman, archer, heavy cavalry*, catapults**
* Can be used as both O and D in strategic formations.
** Some people use their catapults to defend, but its not their primary use.
Builds can vary, and are subjective to your situation. There are no set ratios, and everyonr develops their own. Commonly used builds include;
Axe and Light
Axe and Heavy
220-300 Rams is generally advised, some swear u need no more than 220.
Spear and Heavy
Archer and Heavy
Sword and Archer