Common Roles

Revenge Killer: Thanks to its Speed, Choice Band can be comfortably run to boost Dugtrio's otherwise middling Attack stat and make it a threatening revenge killer. Other damage-boosting items can also be run to bluff Choice Band and not lock it into a move.

Suicide Lead: In matchups where it struggles as a revenge killer, Dugtrio can still function decently well as a suicide lead. Arena Trap can trap foes into potentially undesirable first-turn matchups, and with Focus Sash, its high Speed means it can usually set Stealth Rock and get off a damaging move or create momentum with Memento before it is KOed.

Common Moves

Primary STAB Moves: Earthquake

Setup Moves: Swords Dance, Hone Claws

Utility Moves: Stealth Rock, Memento, Endeavor, Endure, Smack Down, Substitute

Coverage: Stone Edge, Rock Slide, Rock Blast, Sucker Punch, Throat Chop, Foul Play, Shadow Claw

Niche Moves

Stomping Tantrum: When facing teams with Grassy Surge setters, Stomping Tantrum can be run instead of or alongside Earthquake to allow Dugtrio to still do decent damage if Grassy Terrain is up.

Reversal: Reversal is notably Dugtrio's only Fighting-type move and can function similarly to Endeavor when paired with a Focus Sash or Endure.

Common Items

Choice Band: Choice Band is what allows Dugtrio to most effectively lock down and eliminate its teammates' checks or clean up on its own.

Focus Sash: Focus Sash primarily serves as a way to get more than one move out of suicide lead Dugtrio sets, but it can also guarantee it a chance to use a setup move.

Other Damage-boosting Items: Items such as Life Orb and Soft Sand can be used to give Dugtrio a damage boost without locking it into a move.

Niche Items

Choice Scarf: Despite Dugtrio's already-great Speed, a Speed boost from Choice Scarf can allow it to outspeed foes even faster than it and fellow Speed-boosters, catching them off guard. Although its damage is cut by not running a damage-boosting item, it can still trap and remove glass cannons such as Booster Energy Iron Valiant and Choice Scarf Chi-Yu.

Heavy-Duty Boots: Dugtrio tends to be switched in and out a lot, as its low bulk means it rarely wants to be in front of a foe that it cannot KO. Heavy-Duty Boots prevents residual damage from entry hazards building up on it over time.

Tera

Dugtrio does not need to be a Tera Captain, but if you do select it as one, it can benefit from Tera types that boost its offensive capabilities such as Tera Ground, Rock, and types that help its matchup into specific Pokemon it would like to trap and remove.

Draft Strategy

Though Dugtrio is a solid revenge killer, it can often struggle to fit on drafts and should only be drafted to shore up specific weaknesses your draft has. Ground is one of the most valuable typings, and thus it often fits quite awkwardly. Even on teams where it does fit, it's often not worth bringing into matchups that lack foes Dugtrio can easily trap and remove, though at worst it can still act as a suicide lead that can set Stealth Rock and create early momentum.

Wallbreakers: Wallbreakers that struggle against Steel-types such as Kyurem, Latios, and Gholdengo benefit from Dugtrio's ability to trap and remove their checks. Strong special wallbreakers in particular can force foes to invest more in Special Defense, allowing it to do its job more effectively.

Cleaners / Sweepers: Similarly to wallbreakers, cleaners and sweepers that struggle against Pokemon that Dugtrio can effectively remove do well with it on their team. Pokemon weak to fast Electric-type moves like Greninja and Palafin and Pokemon that struggle to break defensive Steel-types like Raging Bolt all appreciate Dugtrio removing their checks.

Knock Off Support: While Dugtrio's ability to force foes to run Shed Shell instead of a preferred item is one of its strengths, it still functions worse as a revenge killer when foes are holding it. Knock Off users like Scizor, Empoleon, and Ogerpon-W can assist it by removing Shed Shell while also acting as defensive switch-ins for it.

Checks and Counters

Grass-Type Pokemon: Grass-type Pokemon resist Dugtrio's STAB moves and do not take super effective damage from any of its coverage moves while also threatening a super effective move back. Ogerpon and Shaymin fulfill this role well, but Rillaboom in particular can cut Earthquake's damage by half by setting Grassy Terrain on entry and threaten a KO back with Grassy Glide.

Trapping-immune Pokemon: Ghost-types and any non-grounded Pokemon are immune to the trapping effect of Arena Trap, and thus disable a key part of Dugtrio's effectiveness. Trapping-immune Pokemon with a type that it usually wants to eliminate such as Gholdengo, Moltres, and Zapdos can fulfill their respective roles while being free to switch out to a teammate that can threaten it.

Faster Threats: Dugtrio's lacking bulk and general reliance on damage-boosting items leave it vulnerable to Pokemon faster than it. This includes Pokemon like Meowscarada, Greninja, and Weavile, which outspeed and deal super effective damage to it.

Priority: Similarly to faster threats, strong priority users also threaten Dugtrio due to its lacking bulk and ease of being revenge killed. Pokemon like Hisuian Samurott, Palafin, and Azumarill all have strong priority attacks that threaten an OHKO on it.

Bulky Attackers: Dugtrio struggles against bulkier Pokemon in general, but ones that can hit it back are an even greater problem for it. Pokemon like Zarude, Hydrapple, and Landorus-T can easily take a hit from it and threaten an OHKO back.