Hi! I'm not a veteran in online battling but I can give you this setup:
Since you do prioritize Talonflame, i'd start with him.
Talonflame @ Life Orb/Choice Band
Ability: Gale Wings
EVs: 124 HP / 252 Atk / 132 Spe
Adamant Nature
- Flare Blitz
- Brave Bird
- U-Turn
- Roost / Steel Wing / Agility/ Will-O-Wisp
Basically, Talonflame doesn't need speed. It just needs enough speed to outrun the faster pokemons. I'll go with Adamant over Jolly. Basically he's a sweeper/revenge killer with this 2 STAB moves, U-turn for switching. I'll be leaving the last move open for your support skill of choice.
Garchomp @ Focus Sash
Ability: Rough Skin
EV: 4 HP/ 252 Atk/ 252 Spe
Jolly Nature
- Stealth Rock
- Fire Blast
- Earthquake
- Protect / Outrage/ Dragon Claw
Basically, Garchomp would be your lead setup sweeper. Stealth Rock support works well with Talonflame as it enables him to OHKO most of the enemy pokemons even those bulky ones. Fire Blast to counter easily grasstype pokemons such as Ferrothorn, Scizor, Forretress and the likes.
Venusaur @ Venusaurite
Ability: Chloryophyll -> Thick Fat when Mega-evolved
EV: 252 HP / 240 Def / 16 Spe
Bold Nature
-Giga Drain
-Leech Seed
-Sludge Bomb
-Toxic/ Sleep Powder/ Hidden Power Fire / Substitute / Sunny Day
I'd go for a Mega Venusaur as your tank, it'll greatly deal an advantage to your team, sapping slowly the enemies health while having your completely full; it synergizes well with Talonflame as Mega Venusaur can counter threats such as Rotom-W and other physical walls.
Sableye @ Leftovers
Ability: Prankster
EV: 252 HP / 252 Def / 4 SpD
Bold Nature
- Fake Out
- Swagger / Recover
- Foul Play/ Will-o-Wisp
- Taunt
He's my worst enemy most of the time, because without proper pokemon with proper damage will leave him pissing you off. He'll be your one of your leads and he'll do perfectly in combating offensive and defensive threats.
Alright for the last 2 since you already have a talonflame (revenge killer, physical sweeper), garchomp (lead secondary support, secondary sweeper), megavenusaur (physical tank), sableye (lead support setup), i'll go for a pure special sweeper and a mixed sweeper:
Empoleon @ Choice Specs
Ability: Torrent
EV: 200 HP / 252 Spa / 56 Spe
Modest Nature
-Hydro Pump
-Ice Beam
-Surf
-Grass Knot / Hidden Power Grass
While most people go for greninja, he's mostly seen as a suicide sweeper, and I don't like that specially that most people nowadays has zapdos or jolteon in their team. I'd go for bulky special sweeper like Empoleon.
Infernape @ Life Orb
Ability: Blaze
EV: 116 Atk / 140 SpA / 252 Spe
Naive/Jolly Nature
-Close Combat
-Fire Blast / Heat Wave / Overheat
-Thunder Punch/ Mach Punch
-Hidden Power Ice / Protect
He'll do good together with Empoleon sweeping the damaged enemy and making you win the game.
Again, this team does not give you a 100% winning rate but would provide enjoyable gaming experience as I myself doesn't go much with the overused pokemons. I hope you try out this team and you might probably like it!

Enjoy! Let me know your feedbacks.
