Treecko is one of those Pokemon that can do everything, but do it in only an average way - it is pretty difficult to predict what it is going to do next, but once you have it figured out, Treecko tends to die quickly. It is pretty quick, but it isn't enough to make it outstanding, it isn't overtly frail, but it isn't defensively competent either. Its movepool is where it excels, but it can only ever carry four moves at a time. It can beat almost any Pokemon in Little Cup given the right moveset, but it never seems to carry the right one at the right time.
All in all, Treecko is a decent Pokemon with some promise, but don't expect him to outperform the more commonly used Pokemon anytime soon. You may well describe him as a small packet of Haribo - he is versatile in flavor, but lacking in substance.
There are several ways that Treecko can be used in the lead spot, and this variant is perhaps the most useful, and almost certainly the most conventional of all of them. Leaf Storm is its basic STAB move, and due to Treecko's above average Speed and Special Attack, it is a good move for hit-and-run attacks against most Pokemon in Little Cup, especially if you can get Treecko into Overgrow range. It also happens to score super effective damage against a good number of common leads and even those that resist it cannot usually afford to switch in safely. Hidden Power Fire gives good coverage alongside Leaf Storm and also 2HKOs lead Bronzor, as well as OHKOing Snover. GrassWhistle is an interesting move that, while having a quite unreliable 55% accuracy, can be used to incapacitate a member of the opponent's team that Treecko cannot pass through, or to prevent a slower Pokemon such as Bronzor from setting up. GrassWhistle is also of particular note against Machop leads, against whom GrassWhistle is guaranteed to hit thanks to Machop's ability, No Guard.
In the last slot, Quick Attack is a useful tool to finish off any slower Focus Sash leads, and is also useful later on in the game if revenge killing is required. Focus Punch, on the other hand, can be used alongside GrassWhistle to buy free turns in which to charge up a punch, and can be rewarding if Treecko happens to catch a Munchlax attempting to soak up a predicted Leaf Storm. Focus Sash will save Treecko if it happens to fall on the wrong end of an attack that would normally OHKO, which is helpful as it will simultaneously activate Overgrow, adding to the raw power of Leaf Storm. The given EV spread generates maximum Special Attack and Speed while also giving an extra point in HP. Because Hidden Power Fire necessitates an IV of 30 in both Speed and Special Attack, an extra 4 EVs are required in both stats to max them out – if you do not run Hidden Power Fire for whatever reason, you can add 72 EVs to Attack instead to gain an extra point there – something you cannot do if you run Hidden Power Fire. A Hasty nature is used so as not to spoil the power of either offensive stat, though Treecko's defensive prowess is not spectacular regardless.Team Options & Additional Comments >>>
Treecko's Choice Specs Leaf Storm is very powerful, though it's a shame that so many Pokemon resist it, as otherwise it could be quite the force. Treecko has a pretty good physical movepool, with access to Swords Dance, Seed Bomb, Quick Attack, Brick Break, Rock Slide, Aerial Ace, ThunderPunch, and Crunch, but Treecko's low Attack stat means that that sort of role is better delegated to other Pokemon. Treecko is perhaps the premier user of Endeavor + Counter sets in Little Cup, whereby it takes a physical hit, survives with Focus Sash, and KOes the opponent with Counter, or else uses Endeavor + Quick Attack if they are faster and likely to use a special move. Endeavor and Counter are, however, illegal with GrassWhistle and Leaf Storm. Also, with the influx of priority users in Little Cup, this strategy is not as effective as it may seem on paper. Lastly, Agility is a nice move which boosts Treecko's Speed, and can be used alongside Swords Dance, or Substitute and a Petaya Berry, which also takes advantage of Overgrow.
Leech Seed can be used to stall out a slower opponent such as Bronzor or Munchlax, while shuffling them and hopefully racking up entry hazard damage as well. Hidden Power Ice is an alternative to Hidden Power Fire, hitting Dratini, Gligar, and Taillow rather than Bronzor, Snover, and Paras for super effective damage. Hidden Power Rock hits Taillow, Snover, Houndour, and Paras rather than Bronzor and Croagunk. Giga Drain can replenish lost health, albeit not by much. Protect can be used on the Lead set to block Meowth's Fake Out. If you are feeling confident, Treecko can use Synthesis to offset Life Orb or Substitute damage on a sweeping set. Lastly, Aerial Ace is an option to take down Croagunk and Machop with assurance, and is also useful against other Grass-types as well as Bug-types.
Treecko has a decent Speed stat, which can be a real asset to overcome his less-than-impenetrable defensive stats, so max Speed is usually the best course of action on any set. Remember that if Treecko runs Hidden Power Fire, it will need 200 EVs to max it out due to having to run a 30 Speed IV – without it it only needs 196 EVs. Next you should aim to max out the primary attacking stat, both of which max out with 236 EVs, or 240 EVs if it runs Hidden Power Fire. When going mixed it is recommended that you max out Treecko's better Special Attack anyway, as Treecko needs all the power it can get. This will leave you with 68 EVs left over, of which 36 EVs are sufficient to get an extra point in HP. If Treecko does not run Hidden Power Fire, you will have 76 EVs left over, which will give Treecko an extra point in any of Attack, Defense, or Special Defense. If Treecko holds Life Orb, it should run a 0 HP IV to minimize the recoil. Lastly, when using a set with Counter, you should aim to minimize Treecko's Defense stat in order to ensure the maximum possible damage done.
Checks and Counters
Treecko is rather versatile, and you should never underestimate its ability to surprise you. Although a total of seven different types resist its STAB, the number of moves it can potentially run can always catch you off-guard. Once you have figured out the moveset, Treecko is a lot easier to handle, if it isn't already dead.
Fire-types such as Houndour and Magby are usually the best switch-ins, as they have useful resistances to both Grass- and Fire-type attacks, but you must be wary of a surprise Hidden Power Rock. In the same vein, Flying-types such as Taillow and Doduo also resist Grass and can attack back with their STAB attacks, though if they are weakened by enough residual damage, they may well find themselves either in Quick Attack range or dying after their attack. Gastly and Stunky both resist Grass - Stunky can be rid of Treecko either by Sucker Punch or Pursuit, while Gastly is faster and is immune to Quick Attack. Dratini is another Pokemon that resists both Grass and Fire, and can set up a Dragon Dance sweep if Treecko attempts to flee, or else beat Treecko with ExtremeSpeed.
On the special side of things, Munchlax is probably the best check you can find. With enough Special Defense to take Energy Ball and a resistance to Hidden Power Fire and Ice with Thick Fat, as well as the ability to OHKO with Fire Punch or Return, it easily beats Treecko. Bronzor is weak to Hidden Power Fire, but resists nigh-on everything else Treecko has and has the defensive stats to take several attacks and KO back. Treecko is quite frail and is easily revenge killed, even factoring in Quick Attack - although Croagunk cannot take Hidden Power Fire, it can usually beat Treecko with Fake Out + Vacuum Wave, and can come in on any STAB attack with its Grass resistance. Treecko is not as fast as it would like to be either, and there are a number of Pokemon that can outrun and OHKO it, such as Elekid, Taillow, and Staryu, although these have to watch out for Agility variants of Treecko. Phanpy deserves a special mention as it can sometimes lure out Treecko and destroy it with Ice Shard.
Remember that none of these checks are complete counters in any way - even granted a resistance they can be stopped on the switch by a surprise set, so always be on your guard.