Mirage Dragon is a great addition to all dragon type decks, it prevents enemy from activating cards such as Mirror Wall and Windstorm Etaqua and saves your monsters from being destroyed. Since it's a Light monster, it has a synergy with Darkflare Dragon summoning condition.
Hunter Dragon can be obtain from Dragonic Force structure deck, a vanilla monster with 1900ATK if "Mountain" is on the field. A DARK monster that can help with Darkflare Dragon summoning condition and since it's a normal monster, it gives Order to Charge and Knight of the Red Lotus more synergy with the deck.
Hieratic Dragon of Nuit is also a great addition for this deck since it can special summon normal monsters from your deck, making it more thin and can give you an aditional tribute monster for Wattail Dragon or even Darkflare Dragon.
Once you have enough monsters on the Graveyard, a LIGHT and DARK monster, you can special summon Darkflare Dragon easily. It can also be used to send more Normal monster in your hand and deck to provide more resources for Knight of the Red Lotus summoning condition, while thinning your deck faster.
Soul Resurrection can special summon any Normal monster from the graveyard, a great card to give more support for this deck.
Dragon's Rebirth is a trap Kidmodo Dragon, it can special summon a Dragon from your hand or grave by tributing 1 dragon from your side of the field, be mindful that the tribute monster will be removed from play and might not be useful for Darkflare Dragon or even Knight of the Red Lotus summoning condition.
Mirror Wall is simply used as a trap card to destroy any attacking monster.
Other useful cards
For versatile cards which can be used in any deck, check the link below!
Lol It's a F2P deck. You don't exactly need a copy paste version. Spell/Traps there can be exchanged lol
Guys, i need your help. I really would like to have lotus, megafiend and darkflare in one deck, what would you change, any suggestions? i know this deck is not so good but i'm kinda stuck. Thanks for your help :)