J.T.

It really just depends on the rest of the team you have around it. You can run it as a stealth rock/supporter, a physical wall, or just a bulky wallbreaker. Personally I'd go with an adamant bulky offensive set but again it's up to you and depends on the rest of your team

If you're not using Torchic because it's a crutch then you probably shouldn't use Greninja either, since you can argue that it's a crutch in its own right. So out of those two I'd go Chesnaught, but it probably won't be very useful in the early game and is a steep drop-off from the other two you mentioned

Try checking the walkthrough

Walrein?

Charge Beam on Ampharos is an option

If you have a focus sash, something with perish song or destiny bond can easily cheese it (or prankster perish song murkrow). If not, try paralyzing it (sturdy/prankster + thunder wave works well) which would allow you to outspeed and kill it eventually with the rest of your team

Personally, I used Noivern in my first playthrough and once I got choice specs it tore through a lot of mons especially with its high speed. Also the ability to learn fly was convenient and I would swap it out with a tm when I needed it. It's really just up to preference though, as Gyarados is insanely good with dragon dance + moxie

You could try Noivern; it gives your team some much-needed speed, you don't have a dragon type either, and it would balance out your team as three physical and three special attackers

Gotcha. I would offer to trade but I'm not online here very much so it would probably be better if you traded with someone else

Just use a link stone on it while it's holding the necessary item

Yeah they're just there for the visual effect

Gible and Deino can both only be obtained basically at the end of V12 and Honedge is currently unobtainable so unless you've beaten all of the gyms you can't get any of them.

Can anyone trade me a Mudkip with good (20+) IVs and an adamant nature? I'll gladly a few perfect IVs if you're feeling generous. Thanks

Once the city is restored there will be move tutors where Mosswater Factory used to be in Peridot Ward