dubble

I ran three eeveelutions at first but quickly replaced them. The biggest problem is that their movepool is bad without TM's. You basically get zero coverage, only hidden power and for that you need the correct IV's - and even then it's only 60 base power without stab. Jolteon is severely crippled by only learning Thunder (miss) and Discharge, both of which suck especially for double battles. Sylveon only gets Moonblast and later Hyper Voice, both not really worth it as its speed is also somewhat subpar. Espeon was definitely OP until about level 50. Then replaced it with Alakazam, which I then replaced by Gardevoir just for the extra coverage.

There are a couple of move tutors, don't bother with it though as they all teach garbage before the city restauration (then you get some nice moves like Hyper Voice for Sylveon/Gardevoir). If you can get a strong psychic type you basically oneshot everything but his dark type with psychic. Espeon by wonder trade for example. Alternatively, Gothitelle (just 3 more levels) with an X-Speed should do the trick too, even if it's a rather poor poke. You should also really get a Fire Stone for Growlithe. Other than that I refuse to run anything below 80 base speed with a speed nature, but that might just be me. You also have a Starmie, which would be about the best pokemon you currently have.

Used EV trained (252 Speed, 252 SpA) Espeon, Alakazam, and Jolteon and that was the fight. Oh yeah, and Blaziken to 1hit-ko it, obviously, as you live a hit and outspeed after one Speed Boost. 390 base power move (130 + stab + very effective). Other than that you can use wonder trade where you sometimes get Mimikyu (Destiny Bond/Perish Song) or Gible. Garchomp only outspeeds on Jolly nature but at that point you already have access to the nature changer.