Chests appear in order of victorys.1bronze,2silver and 3 gold. To get silver chest,you must have one chest no open(but count down finished).Then win 1 battle,open the last chest and you must win another battle. If you win,you will give silver chest.Then wait that chest count down finish,open it,win another battle and the next chest will be gold.If you lose any battle, it will appear bronze chest always.