Pokemon Platinum Team-
This is the team I would recommend if you chose Chimchar as your starter. As for how this will work, I will list the Pokemon with their recommended held item and give you three strongly recommended moves on it, followed by the fourth slot being filled with many different move options that you can choose between, as well as explanations and descriptions for why the moves were chosen. Lastly, I will follow up with the ability that I recommend and then finish up with the location that you can receive this Pokemon, and their evolution methods.
This is personally my favorite of the 3 Pokemon Platinum teams that I have created on this site, since Infernape is my favorite of the Sinnoh starters. But without further ado, let's begin.
Here are the Pokemon that will make up this team-
Infernape, Roserade, Vaporeon, Staraptor, Luxray, Garchomp
Infernape- (Expert Belt)
Flare Blitz/Fire Blast/Blast Burn/U-turn/Rock Slide/Grass Knot/ThunderPunch/Aerial Ace
Infernape sports an impressive base 104 Attack and Sp. Attack stat, backed up by a blazing base 108 Speed stat, with a very wide movepool to boot. This makes it an ideal choice for a mixed sweeper, and the moves that I will recommend are used for that purpose. Flamethrower is the Fire type STAB of choice as it is quite powerful and has no drawbacks. Close Combat is the Fighting type STAB of choice, as its arguably the best Fighting type move that Infernape gets. Shadow Claw is a very solid coverage move on Infernape, with it nailing its Psychic weakness while also providing perfect neutral coverage alongside Close Combat. The last move can be whatever attacking move you want. Flare Blitz is a physical Fire STAB that is pure power with the cost of recoil. Fire Blast is also very powerful but somewhat inaccurate. Blast Burn is the most powerful move that Infernape can learn, but comes with a recharge period after use. U-turn can be used for scouting, or Rock Slide can be used for the potential flinching, as Infernape is very fast. Grass Knot can cover its Water and Ground weaknesses, or you can opt for ThunderPunch which can be used to cover its Water and Flying weaknesses. Aerial Ace is a filler move that is nice since it has perfect accuracy. The only ability Infernape has in this game is Blaze.
Location: Starter, pick Chimchar, given by Professor Rowan on Route 201. Evolves into Monferno at level 14, then Infernape at level 36.
Roserade- (Choice Specs)
Energy Ball/Giga Drain/Grass Knot/Weather Ball/Hidden Power/Leech Seed/Toxic Spikes
Roserade has an outrageous base 125 Sp. Attack stat, with great base 105 Special Defense and good base 90 Speed to compliment it, combined with a decent special movepool, which is why its an ideal Pokemon to hold the Choice Specs. For the first move, Petal Dance is the perfect Grass type STAB move for Roserade alongside the Choice Specs. Roserade is already locked into using the move regardless, so slapping on the Choice Specs gives it a free 50% in power. Sludge Bomb is the second move, as it is Roserade's Poison type STAB move of choice and pretty powerful to boot. Shadow Ball is the third move and provides coverage against Roserade's Psychic type weakness, and it can be very handy against Elite Four Lucian. The last move can be pretty much whatever you wish. Energy Ball can be used for power (while still being able to switch out), Giga Drain for health recover, or Grass Knot can be used to deal with heavy Pokemon. Weather Ball can be used for its versatility. Hidden Power, if you get a good one (such as Fire, Ground, or Ice), can also be used as a coverage option. Leech Seed can be used to deal with an annoying tanky Pokemon, and Toxic Spikes can be a nice utility move. As for the ability, I would recommend Natural Cure, although Poison Point isn't bad in game, so it really isn't that big of a deal.
Location: Route 208, catch as a Roselia. It's easier to raise from a Roselia than a Budew. Use a Shiny Stone on Roselia to evolve it, preferrably at or after level 40, as that's when it learns Petal Dance.
Toxic/Protect/Substitute/Acid Armor/Haze/Aqua Ring/Heal Bell
Vaporeon is a tank that can deal out a lot of special damage, a great Pokemon to hold the Leftovers. It's 130 base HP, 110 base Sp. Attack, and 95 base Sp. Defense are just a testament to the previous statement. Therefore, these are the following moves that I would recommend for it. Surf is the main Water type STAB move, as it is very powerful and an incredibly useful HM move. Ice Beam is the next move, a very nice coverage move that will cover its Grass weakness as well as hitting Dragon types (such as Cynthia's Garchomp) very hard. Hydro Pump is what I would recommend in the third slot, since sometimes you might want a bit more power than Surf can offer, and it will hit very hard. For the last slot, I would recommend some sort of utility move, since Vaporeon has great tanking prowess. Toxic can be used to whittle Pokemon down, Protect can be used for some Leftovers recovery, or you can use Substitute for scouting. Acid Armor raises Vaporeon's weaker Defensive stat, or Haze can cancel out opponent stat buffs. Aqua Ring can stack with Leftovers for even more recovery, or Heal Bell can be used if some other Pokemon on your team is suffering from a status ailment. Vaporeon's only ability in this generation is Water Absorb.
Location: Hearthome City, from Bebe, received as an Eevee. To evolve Eevee into Vaporeon, use a Water Stone.
Staraptor- (Amulet Coin)
Brave Bird/U-turn/Aerial Ace/Heat Wave/Ominous Wind/Endeavor/Roost
Staraptor is fast and furious. Between its amazing base 120 Attack stat and great base 100 speed, it hits like a freight train. I couldn't really think of a good item for it, so I gave it the Amulet Coin, and since this is meant to be an in-game team, this item is great because it doubles the money you get after the battle. Fly is the main Flying type STAB move that you should pick, as it has good power while also being an incredibly useful HM move outside of battle. Close Combat is the second move, and provides great coverage, hitting its Rock and Ice type weaknesses for SE damage, as well as hitting Steel types (who would otherwise resist it) super-effectively. Return is the Normal type STAB move of choice because it is very powerful (102 power maxed out) and has no downsides. Staraptor has an interesting movepool, so that last move could pretty much be anything. Brave Bird will hit the hardest out of all of its moves, U-turn is for scouting, or you can go for Aerial Ace, which will never miss. Heat Wave can be a fun move to mess around with due to potential burning of the foe, or you can go with Ominous Wind to play around with a potential all stats buff. Endeavor can be used if you are low on health to bring the opponent down to your HP, or Roost if you want to recover your health. Intimidate is Staraptor's only ability in Platinum.
Location: Route 202, catch as a Starly. Starly evolves into Staravia at level 14, and Staravia evolves into Staraptor at level 34.
Luxray- (Zap Plate)
Superpower/Elemental (Ice/Fire) Fangs/Signal Beam/Thunder Wave
Luxray is an Electric type with solid attacking stats. Despite many people complaining about its supposedly low Sp. Attack, it's Sp. Attack sits at a very solid base 95. It's Attack stat may be quite a bit higher, sitting at a magnificent 120, but that doesn't mean that you can't give it any special moves. This is why I would recommend the first move you give it to be Thunderbolt, which has good power and will do a lot more than Thunder Fang would. Spark is the second move of choice, which has decent power, but unlike Thunder Fang, has 100% accuracy, so I would recommend it over that, so that way Luxray can have a physical STAB move. Crunch would be the third move I would recommend, as it is a neat coverage move that will be very useful against Elite Four Lucian. Luxray has quite the shallow movepool, so you don't have very many options for the last slot. Superpower is probably the best move to have here, as it provides very good neutral coverage alongside Crunch. Fire/Ice Fang can be used, but keep in mind you have to breed for those. Signal Beam can be used due to the confusion chance but is inferior to Superpower. Thunder Wave can be used for utility if you don't want an attacking move in this slot. For the ability, definitely go with Intimidate over Rivalry.
Location: Route 202, catch as a Shinx. Shinx evolves into Luxio at level 15, and from Luxio into Luxray at level 30.
Garchomp- (Life Orb)
Crunch/Dragon Claw/Fire Fang/Brick Break/Aqua Tail/Draco Meteor/Swords Dance
Garchomp is a beast. As a psuedo Legendary Pokemon with a base stat total of 600, it has no outright bad stats. Most of its stats are quite good, especially its absurd base 130 physical Attack, and excellent base 102 Speed. As such, I would recommend you give Garchomp a mostly, if not completely, physically dedicated moveset. Outrage is the Dragon type STAB move of choice, with a ridiculous 120 base power, it will tear anything that doesn't resist it to shreds. To take care of Steel types that do resist said move, Earthquake is Garchomp's Ground STAB and second move. The third move will be Stone Edge, as that creates the infamous EdgeQuake combo, which boasts very wide neutral coverage. The last move is personal preference. Crunch can be used for coverage, and once again is very helpful against Elite Four Lucian. Dragon Claw can be used if you want a reliable Dragon STAB that you aren't locked into. Fire Fang or Brick Break can work if you want more coverage against Steel and Ice type Pokemon. Aqua Tail is a filler move that can be fun to use. Draco Meteor can hit hard due its absurd base 140 power and Garchomp's respectable base 80 Sp. Attack. Or you can go for Swords Dance to make Garchomp an unstoppable wrecking ball of destruction. Sand Veil is Garchomp's only ability in this game.
Location: This one is actually kind of tricky. You can get in the Wayward Cave early on, but keep in mind that you will have 6 Pokemon before the 3rd gym if you do so. Therefore I would either recommend catching a Gabite at Victory Road, or if you catch a Gible at Wayward Cave, leave it in the Solaceon Daycare up until the final gym or until it reaches level 45 or so. Gible evolves into Gabite at level 24, and Gabite evolves into Garchomp at level 48. However, I strongly recommend either putting Gible in the Daycare until it reaches level 45, or catching a Gabite in Victory Road, do not train up a Gible by yourself, it is a real hassle, since you will have 6 Pokemon on your team very early in the game if you do.
Here it is, my favorite Pokemon Platinum team!