public class AccountWrapper implements Comparable
{
    public Account acct { get; set; }
    
    public AccountWrapper(acct)
    {
        this.acct = acct;
    }
    
    public Integer compareTo(Object compareTo)
    {
        Account compAccount = (Account)compareTo;
        
        if(acct.Total_Contacts__c > compAccount.Total_Contacts__c) {
            return 1;
        } else if(acct.Total_Contacts__c < compAccount.Total_Contacts__c) {
            return -1;
        } else if(acct.Total_Contacts__c == compAccount.Total_Contacts__c) {
            if(acct.Total_Contacts__c == 0 ) {
                return 0;
            }else if(acct.Contacts[0].CreatedDate > compAccount.Contacts[0].CreatedDate) {
                return 1;
            } else if(acct.Contacts[0].CreatedDate < compAccount.Contacts[0].CreatedDate) {
                return -1;
            } else if(acct.Contacts[0].CreatedDate == compAccount.Contacts[0].CreatedDate) {
                return 0;
            }
        }
    }
}

List<AccountWrapper> wrappedAccounts = new List<Account>();

// query your accounts/contacts and in the contact query sort 
// by CreatedDate DESC so the first contact in the list always 
// has the latest CreatedDate.
for(Account account : [select Id, Total_Contacts__c, (select CreatedDate from Contacts order by CreatedDate DESC) from Account])
{
    AccountWrapper wrappedAccount = new AccountWrapper(account);
    wrappedAccounts.add(wrappedAccount);
}

wrappedAccounts.sort();  // custom sort

// extract your sorted accounts into a list of accounts
List<Account> sortedAccounts = new List<Account>();

for(AccountWrapper wrappedAccount : wrappedAccounts)
{
    sortedAccounts.add(wrappedAccount.account);
}