There's really only one combo that I know well with this deck.
D/D/D DIMENSION SUMMON
- Hold out for your hand to have the following cards: Swirl Slime, Nighthowl, 1 Lvl7 D/D/D, 1 D/D/D (DIFFERENT THAN THE Lvl7)
- Activate Swirl Slime from the hand, and fusion summon Dragonbane King Beowulf using itself and your Lvl7 D/D/D
- Activate Swirl Slime in the GY, and special summon the other D/D/D in your hand.
- Normal Summon Nighthowl and use its effect to summon the Lvl7 D/D/D From your graveyard
- Synchro Summon High Gust King Alexander
Now, you should have Dragonbane King Beowulf, a random D/D/D monster, and High Gust King Alexander with 6000 Atk on the field.
If your opponent has counter cards, then you can always wait for the card you need to be drawn again.
You can also perform a similar combo using D/D Berfomet, using its effect to change Nighthowl to Lvl6.
Also, it doesn't have to be Gust High King Alexander for this combo, it could be a different synchro.
Feel free to experiment with different cards to make the most effective combo.