The main strategy is destroying Water Dragon with card effects to revive the monsters used to summon him. Then use Bonding H2O to special summon another Water Dragon.
Stall with any of your level 4 monsters in attack position.
Destroy an opponent's monster with Hydrogeddon to special summon another copy from the deck.
Special summon Water Dragon with Bonding H2O and then immediately destroy him with Destruct Potion or Tribute to the Doomed. Use this combo as often as possible.
Do not discard Bonding H2O for Tribute to the Doomed's cost.
When you have 3 Bonding H2O in your graveyard and 2 effect destruction cards, use Jar of Avarice to return them to the deck. Destruct Potion is preferable to Tribute to the Doomed because it does not need a cost and waiting a turn is not a problem.
I'm not sure, nor have I tried farming for this uninteresting mat. But I think WD cluster doesn't work since it's special summoning and you need to use it's generic summoning method to farm a mat. That's what I feel about farming monster's game mat in this game.
I highly doubt it. Most of them only work for proper Summons, which Cluster is not. I did it with Bonding H2O personally. (It's not that hard, actually. Just keep destroying the Water Dragon you Summoned with cards like Destruct Potion, reviving the materials, then use Bonding again.)
Just a heads up, but flip summons do not seem to count, so Gonogo farming or similar will not work. I believe you need to summon with a Bonding Spell.