New Save File Boys Help A Boyo Out

[Plot Armor]

So I'm thonking of taking away another week and a half of my life replaying this game again [for story reasons] despite having annoying puzzles every time and I ddunno I have no clue for a team or my starter so I'll let you guys discuss and take a crack at it for me.  Any advice at the start is also great.  Teams can be weather, terrain based whatever have fun with it.  I think with this trainer though she'll like strength over everything else so maybe a hyper offense team?

[Waynolt]

As pure offense, imho Leavanny and Flygon are good choices: they resist types that they are super effective against (they can switch into them and take them out with few issues).
Also Sharpedo is good at finishing teams off, thanks to Speed Boost.

I also like Mamoswine (with Ice Shard), Magnezone, and Drapion.
Azumarill too; got one in a wonder trade and it was very powerful (though I didn't like the mon itself ).
Any mon with Toxic is also nice against self-healers (Toxic will eventually take them out). Heal Block can fill the same role, but I happen to like the mons with Toxic more.
And Cinccino with King's Rock is a pain to deal with (I'm sure you already knew this).
And many many more (Gardevoir, Blaziken, etc)... making an hyper offensive team isn't too hard, the problem is that its only tool is a hammer (and when all you have is a hammer, every problem tends to look like a nail).

Then there are the pseudolegendaries and mythical mons, but they're mostly obvious choices (and appear so late in the game that they're not very impactful).

[Candy]

similar to azumarill, I find that unburden slurpuff with belly drum is a destruction machine xD only downside is lack of coverage moves, so run from poison or steel types.

if you want a hyper offensive starter, I think blaziken or greninja are the standard ones that smell offense, maybe charizard can work well as well

if you get drilbur in the mystery egg, you'll have a broken mon on your side fren

[Lil' Sunny]

Charizard, Infernape and Blaziken are perfect for hyper offensive teams.

 

Mamoswine is a wrecking ball with STAB priority, natural earthquake and can even learn blizzard by level up if you really need something to change certain fields . 

 

Magnezone might take awhile to get, leaving you stuck with Magneton for awhile but its worth it for a stupid high special attack stat good bulk and great typing

 

if that's not your thing Galvantula is a great choice too and it can be got early if you know where the event is. Sticky Web and naturally learning Discharge and Bug Buzz is fantastic

 

Budew might start weak and take awhile to train properly but Roserade is a monster later on.

 

Finally if you get the Pachirisu event at the start over Zigzagoon. it's Nuts (pun totally intended). Volt Absorb giving it an electric immunity, Nuzzle for guaranteed paralysis, sweet kiss for more infuriation. Super Fang can help against tankier foes. even learns discharge later if you want some more power behind it. its offensive stats are garbage and it WILL eventually fall off. but its a nice utility pokemon to have early. maybe even late for a few battles if you want it. 

[Monochrome_Complex]

Budew evolves early on if you're feeding it snacks/playing during the day/walking a bunch,  you should be able to get roselia before the first PULSE. Roselia is STRONG,(100 special attack for a mid-stager is pretty awesome) and gets giga drain at 24 or 25, but she can have it  before the 2nd badge without breaking level cap which makes her very strong early game and still effective mid-game too. She's a bit frail physically though so watch for that, plus she's not too good against certain types. You can evolve her before aya too.