This is a very old article so forgive me if there's some noobish stuff =D
"Gadgets?Who uses those monsters? The highest attack they have is 1400!"Says the common duelist.
What are gadgets?
Green gadget:
When you Normal Summon or Special Summon this card,
you can add 1 "Red Gadget" from your Deck to your hand.
Red gadget:
When you Normal Summon or Special Summon this card,
you can add 1 "Yellow Gadget" from your Deck to your hand.
Yellow gadget:
When you Normal Summon or Special Summon this card,
you can add 1 "Green Gadget" from your Deck to your hand.
What makes them special and worth using?
Their effect is the answer.
Its to be sure that you have a +1 card advantage over your opponent and as you have seen after reading the effects gadgets make that happen.
How to cover up their weakness?
Gadgets as you know lack offence,They have to be used in a special way.
Possible cards that help gadgets:
Shrink:
Select 1 face-up monster on the field.
The original ATK of that monster is halved until the end of this turn.
It can be used to save them from an attacking mosnter
Book of moon:
Flip 1 face-up monster on the field into face-down Defense Position.
Can be great in stall needs(Jinzo)
Bottomless trap hole:
When your opponent Summons a monster(s) with an ATK of 1500 or more,
destroy and remove from play the monster(s).
If you dont let your opponent summon what gives you the idea he's gonna attack?(Works really well with green gadget cause your opponent needs to summon a monster with 1500 points to destroy it.
Ultimate offering + Limiter removal = OTK
This is a commonly used combo which allows you to use ultimate offering to summon a gadget..now because you have another one in your hand because of the first ones effect you can get naother to your hand and ultimate offer it

Once you have a field of gadgets BAM a limiter removal and their attack is doubled.
Double summon can also be used as a substitute for ultimate offering.
Now gadgets have some big weaknessess too.
Raiou
While this card is face-up on your side of the field, cards can only be added to the hand by drawing them from the Deck.
Also, you can send this face-up card from your side of the field to the Graveyard to negate the Special Summon of 1 of your opponent's monsters and destroy it.
The gadgets being famous for their effects are now useless...
Skill Drain
Pay 1000 Life Points. As long as this card remains on the field,
the effects of all face-up Effect Monsters on the field are negated.
Horus lv6 +8
This card is unaffected by the effects of Spell Cards. During the End Phase of a turn that this card destroyed a monster by battle,
you can send this card to the Graveyard to Special Summon 1 "Horus the Black Flame Dragon LV8" from your hand or Deck.
This card cannot be Normal Summoned or Set. This card cannot be Special Summoned except by the effect of "Horus the Black Flame Dragon LV6".
You can negate the activation and effect of any Spell Cards and destroy them.
Most of the deck relys on quick play. spells.
Now different combinitions of gadget decks have been tried out.
Oppression gadgets
Monarch Gadgets
Gadget Synchro
Oppression gadgets-The point is to not let your opponent special summon,any monster he summons normally theres solemn judgement and bottomless traphole to counter it
So you basically have total control over your opponent and its just a matte3r of time before you win the duel.
Monarch Gadgets-This is a very strange idea,its based on the fact that by the end of your opponents turn he has no monster because its either destroy by attacking a gadget and you shrinking it or by a trap,In your turn you hae 1 mosnter and he has none..thats when you summon Mobius Theslatos or grammarg to destroy any type pf defence he has.
Gadget Synchro-Gadgets being level 4 monsters you need level 4 tuners and cause of the gadgets effect you already have a level 4 monster in your hand..you just need a tuner and you can synchro summon.
Ultimate offering can be VERY useful here.Since you can get both the tuner and the monster on the field in the same turn and synchro summon
A basic gadget deck may look something like this
~Green Gadget x3
~Red Gadget x2
~Yellow Gadgetx2
~Neo Spacian grand mole
~Legendary jujitsu master x2
~D.D Warrior lady
~Breaker the magical warrior
~Boot-Up soldier-dread dynamox2
~Kycoo the ghost destroyer x2
~Sangan
~Shrink x3
~Enemy controller x3
~Book of moon x2
~MST
~Heavy storm
~Smashing ground
~Lightning vortex x1
~Sakuretsu armorx2
~Widespread ruin x2
~Torrential tribute
~Mirror Force
~Solemn Judgement x3
~Bottomless trap hole x2
Overall its a pretty decent and fun to use deck.
Hope you enjoyed my article.
Thank you for your time
