The first question that comes up for red base machinedramon decks is, why no level 4s? how do you digivolve? That's the neat part, you don't hehe. In all seriousness, machinedramon is really flexible with the builds to the point that you can play black base and digivolve with really strong inheritables, red base for a lot of draw power and early play of level 6s, there are even some blue base decks that play blue/black level 4s so you can use Kaiser Nail for making really strong boards.
Starting up with digi-eggs I run 4 Gigimon EX2-001 to combo with Guilmon P-041 ability to draw 2 on 1 attack. This enables you to go for early aggression as well as adding more cards to the hand which is a core need of this build. The other addition of rookies are 2 EX3 Guilmons for consistency and some potential removal of the opponent rookies.
As you can see the deck runs no level 4s which are not needed for this build, since the goal is to draw a lot of cards with Guilmon, Fire Ball and Hero of the Skies effects so you can get at least 5 different level 5 cyborgs to play a EX1 Machinedramon.
The line up of level 5s is pretty standard. Here's the toolbox of the deck, when you play a machinedramon/chaosdramon you choose which cyborgs will be attached as digivolution sources. This allows you to get really strong effects like being able to attack unsuspended digimons, trash security after winning a battle, security+, blocker, reboot, etc. I made sure to run 2 Megadramon from BT9 since there are a lot of 3 cost tamers being played in this format (i.e. Tai, Ai & Mako, Takuya, Hunters, Xros, etc.) and some removal is always nice. Deleting Impmon, Bokomon/Neemon, and memory blockers is also great for this deck. The reason for playing so many at 1 copy is that you can't add cards with the same card number per each effect. This means that if you have 2 BT11 Metaltyrannomon you can only add 1 of them per effect (i.e. if you play a machinedramon). You can maybe add the other one to the stack when you digivolve to Chaosdramon or use other effects, but each effect you activate has to add different cards.
So, the main level 6s of this build are the before mentioned EX1 Machinedramon which are played once you need to pressure your opponent. If there aren't any memory blockers against you and if you have all of the necessary materials, the Machinedramon should cost you 7 memory after the memory gain (you have to make sure to have at least 2 memory or you can't play it, the memory gain doesn't bypass the play cost). Then you get the upgrades in the form of Chaosdramon EX3 and ChaosdramonX BT12 which evolve on top of your machinedramon for a bigger and stronger stack. The main removal of this deck is the De-Digivolve from Chaosdramon which most of the time will allow you to shrink your opponent stacks and attack over them. ChaosdramonX is the boss here, being able to inherit all of the effects from Machinedramon and Chaosdramon which are really strong.
The tamers for the deck are Analogman and Hiro Amanokawa BT8. Analogman is what brings consistency to this deck by letting you cycle through your cards and, it's also one of your defenses by allowing you to redirect any attacks on your security to your level 6 machine digimons. This is even better against Red Hybrid since they have effects that gain memory when you block attacks, however they don't activate when you redirect them. Hiro is the best red tamer you could get for this build, it allows you to play at least 2 of the options we use to draw cards per turn, it grants you enough memory to play your machinedramon, you can use the effect to gain DP. You could run 1 but I like consistency.
The options I played are Hero of the Skies and Fire Ball for draw power (fire ball also allows you to delete the opponent's rookies for 2 cost). DG Dimension is a great card for removal since the effects that grant you immunity to De-Digivolve are extremely rare (the most common is BT11 MetalgreymonX), which will make it easier for you to potentially clear the opponent's board with 1 card. Last but not least, is Attack of the Heavy Mobile Digimon. This card is, in paper, a -1 in cards in hand but compensates by letting you immediately play a big machine, gain rush and blitz and then obtain some advantage (or even attack for game). The security effect is also great allowing you to discard any cyborg or machine to delete any of your opponent's digimon of equal or lower play cost.