Their name, "Gagaga" is from either the pronunciation for the Chinese character they use as a crest, which can be pronounced "ga" in Japanese, or the Japanese manga sound effect "ga" which is used for physical impacts, similar to the English "pow" used in comics. This could be because the "Gagaga" monsters use physical attacks in the anime and manga. All "Gagaga" monsters bear a crest of the Chinese character for the first person pronoun (我) which can be pronounced "wa" or "ga" in Japanese. The crest cannot always be seen on the individual card's artwork though, but can be seen in the anime and manga, usually on the monsters' backs. The male members of the archetype cover the lower part of their faces with scarves, except "Gagaga Child".
The "Gagaga" Spellcasters, "Gagaga Magician" and "Gagaga Girl", bear a striking similar appearance to "Dark Magician" and "Dark Magician Girl" respectively, monsters used by Yugi Muto in the original anime and manga. Both "Gagaga" Spellcasters are 3 Levels lower and have 1000 less ATK than their "Dark Magician" counterparts. They are also all DARK monsters, and are often used by Yuma and Yugi in their Duels. The "Gagaga" Spellcasters also share a "senpai and kohai" relationship, similar to how the "Dark Magicians" shared a master and apprentice relationship.
Despite being weak in terms of ATK and DEF, the effects of the "Gagaga" monsters allow them to change their Levels very easily, resulting in quick and easy Xyz Summons. The effect of "Gagaga Magician" allows him to change his Level from 1 through 8 and the effect of "Gagaga Girl" allows her to copy his Level. This allows them to easily Xyz Summon any generic, Spellcaster specific, or DARKXyz Monster of Ranks 1 through 8. "Gagaga Caesar" also helps in this by using his effect to banish a monster in the Graveyard to change the Levels of all face-up "Gagaga" monsters you control to the banished monster's Level. This allows them to Xyz Summon any Xyz Monsters above Rank 8.
The greatest additions to the deck are "Gagaga Child" and "Gagaga Sister". "Child" is capable of Special Summoning itself from the hand if one controls another "Gagaga" monster, fixing a lack of multiple summons for the Deck, and then copy its Level at the cost of the turn's Battle Phase, but this cost is mitigated by the strong monsters it can summon if used in conjunction with "Gagaga Magician". Monsters like "Evilswarm Exciton Knight", "Number 101: Silent Honor ARK", "Castel, the Skyblaster Musketeer", "Maestroke the Symphony Djinn", "Number 11: Big Eye", "Divine Dragon Knight Felgrand", to name a few, are more disruptive than offensive or have a battle related cost themselves, so they can be Summoned with relatively small consequences.
"Sister" can Search a "Gagaga" Spell or Trap Card when she is Normal Summoned. Examples include "Gagagashield" or "Gagagarush". Her true potential, however, lies on searching cards like "Gagaga Academy Emergency Network" and "Gagagarevenge", which can be used to Special Summon other "Gagaga" monsters, mainly "Magician" to use her own effect that targets another "Gagaga" monster, and makes the Level of that monster and herself the sum of both, those granting access to very powerful monsters up to Rank 10, even without "Magician". Since the other "Gagaga" monsters are Level 3 or 4, this equals to Rank 5 or 6 plays, which can be equally devastating.
Also, a lesser known but still effective tactic is to use the "Gagagas" for a Synchro Summon. Only "Gagaga Magician" and "Gagaga Caesar" cannot be used for a Synchro Summon, as stated in their text, but the rest of the archetype can be used, as they don't have the same restrictions. With their Level altering abilities and cleaver usage of their support, they can be used to Synchro Summon a variety of Synchro Monsters with ease, making the archetype flexible with other strategies. Even though they cannot be used for the summoning, manipulating "Magician" and "Caeser" abilities, which will in turn manipulate other "Gagagas", can help fine-tune their Levels to perform a desired Synchro Summoning. While their true strength lies in Xyz Summoning, they are still useful with Synchro Summoning as an alternate strategy.
"Gagaga" monsters however suffer from lack of speed. A good way to mitigate this is to combine "Dododo" monsters in the deck such as "Dododo Warrior" which has a high level and is easily used along "Dododo Witch" and "Dododo Driver" which can perform good combinations, with cards such as "Onomatopaira" that can search key monsters such as "Gagaga Sister" or "Gagaga Magician" (the former is useful if one discards a Magician and searches a Sister to search a "Gagagarevenge" to Special Summon Magician), or cards like "Dodododraw" to draw 2 cards further increasing advantage. "Gagaga Mancer" can also speed up the summoning power by reviving another "Gagaga" monster, though at the cost of not being able to summon any other monsters except "Gagaga" monsters. They also lack raw power for their Levels/Ranks, as the strongest monster of the archetype is the 2100 ATK "Gagaga Head" in terms of printed power (though "Gagaga Cowboy" can have 2500 ATK, but only when in Attack Position and during your turn), which makes them vulnerable to stronger attackers. While "Gagaga Girl's" and "Gagaga Mancer's" abilities, along with "Gagagatag", can help mitigate that problem, they will still be left at a disadvantage compared to stronger monsters with the same Levels/Ranks.