Timid (+Speed/-Atk) or Modest (+SpA/-Atk).
Meowstic is pretty fast, but the speed increase from Timid can make sure you outrun some notable threats. Or, if you feel it's speed is already good enough (It's base 104, so it's pretty decent), you could run the special attack increase since female Meowstic learns more offensive moves.

Beaten to the punch because I had to kill a bug :lol
Oh well.

Wow, i just breeded an Espurr with perfect IV's in Special attack! Now to pull off the breeding trick to get one with a good nature as well.

Breeding trick?

Anyway, if you have a Power Lens, it's only going to take you one egg to make that happen. Slap it on her, get any male species in Espurr's egg group that's Timid or Modest (or a Ditto) and slap an Everstone on it, and you're done!

I have a Scizor and a Gyrados trained up, but I'm unsure which Mega Evo I want to run.

Why not both?

Scizor is great for going on the offensive with speed and access to swords dance (Especially since it has access to sucker punch) and Gyarados is good too with dragon dance to use plus moxie if you get a KO before mega evolving. I say it all depends on what team you need to run it on.

Power Lens, eh? Hmm, that sounds better than a Destiny Knot, and would help me with this Gligar nonsense.
EDIT: Never mind, the Power Lens is not what I thought it was, hehe.

No fiesta for you.

I just need a sweeper Pokemon since I built up too many defensive walls and I don't like stalling to death :lol
My Gyrados has Intimidate, though, so I'm not sure how viable it is for use when it's not going to be mega evolving (Scizor is rocking Technician since I'm not that dim :lol)

Yeah, Klonoa wants a good-natured Meowstic with one perfect IV in Special Attack, no sense messing with the Destiny Knot for a breeding project that simple. Even easier, of course, if you simply have an Espurr Friend Safari, but that's neither here nor there.

Wanting a 5IV Tentacruel in a Heavy Ball, that's a whole other story. ;-;

for netflix user black and white season 14 and season 1 of pokemon will be on netflix by tommrow with 2 movie both of the victinie movies as well