A dime a dozen is something that is very easy to get and is something common.
1. The boss told the peon that if he was going to just sleep on the job he need not come to work at all. The unemployed were a dime a dozen and he could just appoint somebody else.
2. The priest had no problem in getting the required flowers for the puja. As it was the festive season, flower stalls were a dime a dozen.