Keep training!! Buy chests or get train with Warriors(1000 exp) /Archers (10,000 exp) /Gandalf (50,000 exp) from Gollum's Riddle or special events. You may need to lvl up your Great Hall to lvl 10 before reaching lvl 190. Once your hero reaches above 199, 3300+ you can use the last “Train with Gandalf” to reach level 212. HOWEVER, be sure not to go over Level 199, 3960 before using last Gandalf.
You could check out below website to calculate how much exp you would need to gain lvl 212 hero. (some terms may be different.)
http://levelyourknight.com/
http://levelyourknight.com/