A budget deck with Dark Magician, Blue-Eyes White Dragon and Chaos ritual monsters.
Main Mechanic
Bring out your normal monsters fast in order to use them as fusion, ritual or XYZ materials. Summon Dark Magician the Dragon Knight to protect your spells and traps and make it mostly invulnerable with Eternal Soul and Piercing the Darkness, while banishing and destroying cards with Dark Magic Attack, Dark Magical Circle and Magician of Chaos.
Combos
Thanks to Cosmo Brain or Fusion Deployment, you can easily special summon Dark Magician and Blue-Eyes White Dragon on your field from your deck. Cards like Piercing the Darkness or Dark Magical Circle make these summoning count, allowing to draw and banish cards. Illusion Magic and Summoner's Art can search for these same monsters, which can be used to summon Cosmo Brain. Eternal Soul can special summon Dark Magician once a turn.
Cosmo Brain can summon Dark Magician on the field by tributing an effect monster, and go for Ebon High Magician (more defensive) or Ebon Illusion Magician (more offensive).
Chronicle Magician summons itself when Dark Magician or Blue-Eyes White Dragon get on the field and give them a big ol' 2500/2500 boost until the end phase. Combined with Piercing the Darkness, you can easily deal at least 5000 points of damage with a single blow. Chronicle Magician can also be used to go for an easy rank 7 XYZ summoning.
Keeper of Dragon Magic allows you to search for Fusion Deployment, Magicalized Fusion or Polymerization. You can discard a fusion material like Dark Magician, Blue-Eyes White Dragon or Witch of the Black Forest from your hand to activate its effect, then summon it from the grave face-down. Keeper of Dragon Magic makes it much easier to fulfill the summoning conditions of Dark Magician the Dragon Knight.
/!\ Be careful: when using Keeper of Dragon Magic, you can't Link, XYZ or Synchro summon in the same turn. /!\
Dark Magician the Dragon Knight and Eternal Soul make for a great force together, since Eternal Soul make Dark Magicians unaffected by your opponent's effects and can resurrect Dark Magician the Dragon Knight any time. The Dragon Knight prevents your opponent from destroying or targeting your spells and traps. One of the main goals of this deck is to get a board with the Dragon Knight and Eternal Soul active. Piercing the Darkness complete this combo by making your Dragon Knight virtually invincible.
This combo would leave your opponent with a very few possibilities of breaking through : Kaijus, effects that banish/bounce traps without targeting, or this bad boy: Trap Eater.
Magician's Rod can search for any Dark Magician-related spell or trap (except for The Eye of Timaeus uuuuurgh). You can search for Magician's Salvation, activate it and set Eternal Soul directly from your deck. It can also search for Chaos Form or Secrets of Dark Magic to go for rituals or fusions.
You can easily bring out Blue-Eyes Chaos MAX Dragon or Magician of Black Chaos MAX by using Blue-Eyes White Dragon (most likely from your grave) with Chaos Form. Same goes with Magician of Chaos by using Dark Magician. Since Magician of Chaos's name is changed to "Dark Magician" on the field and in the grave, banishing a Dark Magician for its summoning is no big deal.
Magician of Chaos's powerful ability allows you to destroy a card on the field when a spell/trap is activated, making a good combo with Dark Magical Circle. Since its effect isn't a hard "once per turn", it can destroys itself to bring out a Chaos MAX from your hand, be special summoned back from the grave by Eternal Soul and activate its effect again to destroy another card on the field.
Witch of the Black Forest can search for Blue-Eyes Chaos MAX Dragon. Since Chaos MAX Dragon doesn't activate any effect, it doesn't suffer from the downside of the Witch's effect. She can also search for useful monsters for the next turn.
Lighten the Load is here to reduce the risk of bricking.
Magicalized Fusion works well as a late game changer. Fuse 5 spellcasters with different names to leash out Quintet Magician and destroy every card on your opponent's field, and go for a whoopin' 4500 of direct damage. Starving Venom Fusion Dragon can surprise your opponent with a quick fusion by Secrets of Dark Magic and destroy monsters as payback if Eternal Soul gets destroyed.
Master of Chaos is a walking danger who can banish every monster on your opponent's side of the field by tributing Blue-eyes and a dark monster.
Blue-Eyes Ultimate Dragon, Dark Magician Girl the Dragon Knight and Musician King are here for summoning Blue-Eyes White Dragon, Dark Magician Girl and Witch of the Black Forest by the effect of Fusion Deployment or Keeper of Dragon Magic.
Notes
This deck isn't fully optimized and designed to be affordable. There are change suggestions in the side deck.
Take care ♥