Since using Polymerization and 5 Dragon-type monsters can often be not worth it, you can use Dragon's Mirror to make it more viable. You can use any Dragon monsters and when they get sent to the graveyard, use them as the fusion materials for Five-Headed Dragon.
Putting 5 Dragon-type monsters can be pretty slow, but you can make it run much faster by milling yourself with these cards. Magical Merchant can let you fusion summon into Five-Headed Dragon within the first few turns if you get lucky. The same with That Grass Looks Greener, but it can send the spell card to the graveyard. Cards of the Red Stone can be a good and safer approach since you can bring both Red-Eyes B. Dragon and Red-Eyes Zombie Dragon for a total of 6 Red-Eyes monsters.
In case someone says something stupid about summoming this, you CANNOT use Fusion Subs to summon this thing. Fusion subs only work if the Fusion Monster states a specific card name. This card states "5 Dragon type Monsters" which means it can be any 5 dragons. You can fusion summon this using 3 Poki Draco and 2 Totem Dragons if need be.
Extra deck:5 headed dragon
Deck:fill deck with dragon type monsters and polymerization
Skill:draw sense:spell/trap card
Start game with 4 dragons in hand
Don't play anything until you have 5
When you've lost enough life points activate skill
You are guaranteed to get polymerization as that is the only spell u have
Play 5 headed dragon
SRH, Hane-Hane, Man-Eater Bug, Floodgate, Yomi Ship, Exploder Dragon, Michizure... You can get rid of this card so easily, it's a glass cannon, high status but heavy summoning condition and easy to get off the board.
Even if this card isn’t really that great I’ll still use it because I think it’s a cool card. But I’ll probably stick in ranked