Using Field Spell Cards that boost your monster's ATK is the best way to go with this card, as you can summon multiple copies of it quickly and won't need to use Equip Spell Cards on individual "Hydrogeddons". Which Field Spell you use depends on your play style--if you want beatdown, use "Umiiruka". If you plan on Summoning "Water Dragon" you may use either "A Legendary Ocean" or "Jurassic World"; "Oxygeddon" will gain no boost from "A Legendary Ocean", but that Field Spell works well with most WATER monsters and most "Water Dragon" users tend to run WATER-based decks.
Use "Aqua Chorus" in conjunction with "Hydrogeddon", as it will boost the power of multiple monsters that share the same name.
Combine this card with "Umiiruka" and "Aqua Chorus". The first "Hydrogeddon" will have 2100 ATK, and if he destroys a monster, you'll get two 2600 ATK monsters.
Use "Foolish Revival" to get an extra monster to destroy in battle by an "Hydrogeddon", thus getting 3 copies of it in one turn.