Magby is often overlooked because of Elekid, which has fantastic coverage and slightly higher Speed. However, Magby has many advantages over Elekid. Its 120 Base Power STAB attacks easily out-muscle Elekid's much weaker base 75 and 95 attacks. Magby also has Mach Punch, which is far better than Elekid's Quick Attack due to its typing and ability to hit Houndour, a Pokémon who can switch into its STAB for free.
Magby has one huge weakness however: its weakness to Stealth Rock. This makes Magby unable to switch in and out as it pleases, and gives it only 3-4 switch-ins before it bites the dust. Because of this, Magby needs to be played to its strengths, hitting hard and fast, knocking out the opponent before it gets knocked out. With so many Pokémon falling to Magby's powerful attacks, Magby should be considered for almost any offensive team.
Magby has all of the right tools to be a top-notch sweeper in the Little Cup metagame, and this set takes advantage of all of them. Flare Blitz coming off of 17 Attack is especially potent, especially when it's also boosted by Life Orb. With Houndour being around, Magby can take advantage of its priority move, Mach Punch, which easily KOes Houndour while avoiding Sucker Punch. Priority is a godsend in Little Cup, because 40 Base Power is usually enough to finish off any fast and frail foe after taking only minor damage. Magby is also gifted with ThunderPunch, a great tool to rid the battle of Water-types who may switch in, especially Pokémon such as Mantyke, Slowpoke, and Kabuto, who will usually be your opponent's first line of defense against Fire-type attacks. With these attacks, Magby can OHKO a majority of the metagame, while being able to 2HKO even the most sturdy walls such as Munchlax (the Leftovers variant), who is 2HKOed by Flare Blitz as long as Stealth Rock is on the field. Beware of Flare Blitz recoil when you use this set, as it can be deadly for Magby after even two uses.
The last slot is pretty flexible, but Overheat is recommended for its sheer power. With a solid 13 Special Attack stat, a STAB Overheat is still strong enough to OHKO major threats such as Gligar, who could otherwise survive any of Magby's physical attacks, even Flare Blitz. Brick Break is an option to hit Munchlax for the guaranteed OHKO, but leaves Magby open to Gligar. Hidden Power Grass is an option to OHKO Pokémon such as Geodude, Rhyhorn, and Kabuto who would otherwise cause some trouble for this set. However, they are quite uncommon. Overheat is still preferred for that reason, not to mention its ability to get the KO on most of the previously mentioned Rock-types after they switch into a Flare Blitz. Overheat also makes for a safe opening attack due to Flare Blitz recoil.Team Options & Additional Comments >>>
While this set looks similar to the above set, its playstyle is quite different. This set is purely made for beating the opponent's bulky Pokémon down with hard-hitting attacks. Fire Blast is Magby's main attack, giving Bronzor and any Pokémon who doesn't resist Fire-type attacks a one way ticket back to its Pokéball. Here is where the two sets differ; this set can use Cross Chop, ThunderPunch, and Hidden Power Grass in one move set, giving Magby potentially the best super effective coverage possible in Little Cup. Cross Chop is Magby's main tool for getting rid of Munchlax, who is KOed after switching into any other attack, and is OHKOed most of the time with just Stealth Rock in play. Hidden Power Grass takes care of Pokémon such as Geodude and Kabuto, who have the Defense needed to survive a Cross Chop. ThunderPunch takes care of Mantyke, and also gives Magby a reliable way to take out Drifloon.Team Options & Additional Comments >>>
Even with a base Speed stat of 83, Magby is still outsped by a select few unboosted Pokémon and Choice Scarf users. This makes Magby a great candidate for a Choice Scarf, with its respectable Attack stat and great coverage. With Magby's impressive Speed stat, it will outspeed the majority of Choice Scarf users, and even some Rock Polish users such as Rhyhorn. Flare Blitz is Magby's move of choice, dishing out plenty of damage to any foe that isn't resistant to it. ThunderPunch takes care of most Water-types switching in, with the exception of Chinchou. Hidden Power Ice is great in the last slot to revenge kill Gligar, and even hit some of the bulkier Rock-types. Brick Break can be used over Mach Punch with Choice Scarf to revenge kill most Aron (defensive variants can still survive), as Mach Punch won't OHKO. Flare Blitz is illegal with Cross Chop, so you are reduced to using Fire Punch as a main STAB move if you want the stronger Fighting-type attack than Brick Break. If you want the extra punch, Magby can use a Lonely nature as its Speed is already blistering fast.Team Options & Additional Comments >>>
In theory, Magby should be able to pull off an effective Belly Drum set due to its Speed and power. Setting up with Magby is difficult, but not impossible with support from Pokémon such as Wynaut with Encore. However, Belly Drum Magby is actually able to be beaten by some very common Pokémon, even after a Salac Berry (without a Salac Berry, Magby is easily outsped by Choice Scarf users). Since Mach Punch is illegal with Belly Drum, Magby will have extreme difficulty with most priority users. For these reasons, Magby is better off using mixed Life Orb or Choice Scarf sets than an extremely situational Belly Drum set.
The special-oriented wallbreaker set can also be used with Substitute and Focus Punch, which eases prediction and gives Magby an easier time with Pokémon such as Lickitung. However, sacrificing either Grass- or Electric-type coverage is definitely not good, so the listed sets are generally better. Iron Tail is an option for the Choice Band set, 2HKOing Rock-types, but its 75% accuracy leaves something to be desired, and Cross Chop is often a more effective move.
Flamethrower is an option over Fire Blast if you are an accuracy freak. However, Fire Blast guarantees many OHKOs, most notably a KO on Gligar. Similarly, Brick Break can be used over Cross Chop for the sake of accuracy. A special Choice set can also be used, but 16 Special Attack will only get you so far. However, if you like the "hit-and-run" style of play, a Modest Magby's Overheat will deal loads of damage to incoming switch-ins or whatever is on the battlefield. This is made even better by its 27 Speed after Choice Scarf and its ability to carry Cross Chop for Munchlax.
Focus Sash is usable on any set without Flare Blitz as well, giving Magby a chance to usually get at least two attacks on your opponent, and since Magby has such top-notch offensive stats, two attacks is usually enough to KO the average Pokémon.
Magby is one of the hardest Pokémon to switch into due to its excellent type coverage and power. In fact, not one Pokémon can safely switch into Magby without the risk of getting OHKOed or 2HKOed, largely due to a lack of Dragon- and Flying-types to absorb Fighting- and Fire-type attacks like there are in OU and UU. Now Mantyke could switch into any of the aforementioned attacks, but that's where ThunderPunch comes in. The best (or only) way to deal with the Life Orb mixed attacker set is to predict, and send something in that can take a Mach Punch on top of the attack that it switched into. This leaves few options, but the most reliable options are likely Choice Scarf Cyndaquil or Chinchou. Cyndaquil is not hit super effectively by any of Magby's attacks, and can KO with Hidden Power Ground. Chinchou is similar, and it can easily KO with a STAB Surf. Gligar also does well, as it resists both of Magby's non-STAB attacks and is not KOed by Flare Blitz. Overheat has a 2% chance to KO it without Stealth Rock, and a 100% chance to KO it with Stealth Rock, so watch out for a Life Orb-boosted Overheat. It also has a 50% chance of winning the Speed tie with Magby, thus allowing it to come out of the matchup largely unscathed.
The best method to rid yourself of Magby is revenge killing. As long as a Choice Scarf user isn't weak to Mach Punch, you can safely KO Magby with its weak defenses. Aqua Jet users such as Buizel or Squirtle can also quickly douse Magby for the revenge kill. Diglett gets a mention for its ability to trap and OHKO Magby with Earthquake, and it can switch into ThunderPunch unscathed due to its Ground typing.