Note that unlike the original Bitcoin that requires miners to invest in advanced and expensive ASIC mining equipment, Bitcoin Diamond uses X13 mining algorithm which means that you can use even the standard computer GPU.
To raise the chances of confirming more transactions, you should consider joining BCD mining clubs. These are groups of people who come together to consolidate the hashing power and raise the chances of confirming more transactions. Note that the coins mined using pools are shared among the members based on the mining power each contributed.