After a week I managed to reach Chapter 5 - faster than expected though I did skip all the side quests, hence locking myself out of the Fiend Colony, meaning I will not be able to unlock the The End garment grid (boo-hoo) ... why did I missed it in the first playthrough?
Anyway, have now unlocked not only the Aeon Cup (got the Peerless GG already -- hurrah) but also the Fiend World Cup/Almighty Shinra Cup (nabbing the Adamantite along the way). Will do one more Cactuar Cup battle before attempting the Fiend World Cup and unlocking, hopefully, the Almighty Shinra Cup before YRP levelled up more. Yuna, Rikku and Paine are at level 42-43 currently, which is neither too high nor low and battles remain challenging, especially in the Fiend Arena.
I've been fiddling with the setups a bit because I want to stay thematic (like, I don't see Yuna as a physical fighter, more a mage/ healer) while making every character strong and useful. So this is what I have so far (and this is what makes this game fun):
She can switch between Gunner, Songstress, Psychic, Festivalist, White Mage and Mascot, all with maxed abilities. But since Mascot kinda overrides White Mage and Catnip has been nerfed, I've switched out both. Psychic is a real find (teleport and invincibility abilities are amazing) so great to have at the start of a battle (to get behind enemies). Songstress is great for buffing and Festivalist can cast Ultima but probably only good enough for non-boss fights).Lady Luck seems like a good one to explore later... So Mascot is still the preferred dressphere/class for Yuna and when coupled with the Higher Power GG, she can be a v good healer while dealing out decent damage with Moogle Beam. I still have one more accessory slot for her (be great to give her Ragnarok so don't have to worry about running out of MP). I put the stat boosting Adamantite on her. Though that slows her down a lot but it also makes her invincibility and (songs) buffs longer (I think...) which is super cool.
I see her more as a support character, with ability to steal, heal and buff. I switch her between Thief, Berserker and Mascot ... thematically all make good sense. I skip Alchemist cos I cannot do the mixing (cannot read the Japanese names of items!). So she can do damages as Berserker, with auto-regen (though not great) as well as heal and buff with Mascot. I like her because she moves fast (and can steal) and I slapped a Valiant Lustre GG on her to further boost her defence. But she is the weakest of the three... sometimes just use her as bait (for tough boss). I put a speed bracer and ribbon on her for More protection!
I never liked this character (all the pouting... and that hair!) but, boy, is she the best Boss Killer in the game?! I only see her as a heavy damage dealer so Warrior and Dark Knight classes suit her the best. Mascot also has Samurai skills (Fireworks!) which is brilliant. Needless to say, I put the damage-boosting Peerless on her (break damage limit) as well as Iron Duke to boost her stats (monstrous!) and Ragnarok, meaning can keep using her amazing Cactling Gun without the fear of running out of MP.
I need to build these "creatures" ... both have multiple hits so putting Invincible and Catnip on them would work wonders ... will try that later Mwahahaha...