The classic Dark Magician Girl card, while not as strong as other monsters for its level, happens to have a huge amount of support and features more alternative summoning options for getting it onto the field than practically any other card in legal use. Due to the number of ways it can be used, there are multiple deck variants based upon it, any of which can be competitive even against more modern deck archetypes when properly used.
Dark Magician Deck
Having multiple copies of Dark Magician and Dark Magic Curtain leads to summoning the monster in just one turn and then following up with cards that support it such as Dark Magic Attack and Thousand Knives helps to keep the field clear as well reduce the danger of monsters. Having multiple spellcasters that can add their effects as well as Spellcaster Deck Supports such as Old Vindictive Magician, Defender, the Magical Knight or Magical Dimension help as well. Any other cards that are in this deck should revolve around the Dark Magician as far as getting it out on the field and keeping it there. Another effective combo using Dark Magician is sending it to the grave with Elemental Hero Prisma's effect (by showing Dark Paladin) and then reviving it using cards like Birthright or Swing of Memories.fuon't focus on Dark Magician. Penguin Soldier or Neo-Spacian Grand Mole are good monsters for returning annoying or threatening monsters on your opponent's field to their hands. You can also use Royal Decree to stun all trap cards, then you're sure that your enemy will not activate Sakuretsu Armor or Mirror Force to destroy your Dark Magician. Put Destruction Jammer in your Deck as well. It will make sure your Dark Magician does not get Fissure or Lightning Vortexed.Since he is a SpellcasterType you'll can combine with Secret Village of the Spellcasters and Royal Decree to create a spell trap lockdown.
Dark Magician Girl Deck
Similar to the Dark Magician Deck above, the Dark Magician Girl deck focuses on the Dark Magician Girl, while having some focus shared with the Dark Magician and possibly Magician of Black Chaos. Dark Magician Girl benefits from these two being sent to the graveyard, with a 300 ATK boost for each of them. Therefore, it is possible to max out her attack at 5600 by having 3 of each in both players' graveyard. Using cards like Foolish Burial and Armageddon Knight really help in getting those cards to the graveyard quickly. Though not as supported as the Dark Magician itself, the Dark Magician Girl shares some support and can tribute to summoning the Dark Magician as well with cards such as Sage's Stone.Also If you do the math, with 3 dark magician in both players decks you get 3800, And you get 5600 when you get them.
Fusion Dark Magician Deck
This deck focuses on either the fusing of the Dark Magician with either Buster Blader for the Dark Paladin or with Flame Swordsman for the Dark Flare Knight and ending with the emergence of Mirage Knight. In both of these decks helps greatly especially with Dark Flare Knight needing an additional Fusion to fuse with. For Dark Paladin it helps to have cards like Skilled Dark Magician and Skilled White Magician to help search the deck and bring out these monsters faster, as well as to include Dragon-Type monsters to boost the ATK of Dark Paladin. The overall goal of said decks would be to bring out the two fusion's faster and use their effects to devastate the field or gain a quick lead. You can use DNA Surgery to make the monsters Dragon-Type monsters in order to increase the ATK of Dark Paladin.