A Good Felicia Build?

It's kinda hard to make her an "all around" unit because her stats aren't necessarily the best for anything other than countering mages and nuking units with Glacies bombs.

Felicia's Plate is an obvious choice of weaponry for her. You could go with the effective refine if you wish, but I think a speed or resistance refine could also work to her advantage.

The rest mostly depends on how you'd want to build her. Fury and Desperation work for nuking, other enemy phase skills such as Steady Stance, or Distant Defense, is good for enemy phase mage tanking.

I have Felicia+6 ally supported with Nowi. Several things I can say:
- It's not a problem if she focuses on fighting mages. That's what she's best at. However, you might want a bit more out of her if you want to merge her 5*+10.
- Generally speaking, since she has a lot of stat points allocated to spd, she prefers to fight fast units who don't have as many stat points allocated to mixed defenses.
- In PvE you want flashing blade or infantry rush support. They just have way too much HP, so you want to be firing off glacies as often as possible. Atk smoke is a great choice for C-skill to just blunt their attack so your tanks can shield her.
- If IS continues the direction they're going with inflated stats, Felicia is going to lose value as an offensive unit because getting through the ridiculous amount of HP more or less requires a big atk stat (i.e. the glacies might not be enough if they have 80HP. You can get sometimes 20 damage per shot, maybe a bit more especially if you stack buffs, but glacies will score for maybe 30-35 extra damage depending on merges and buffs), plus even their weaker defensive stat can get into the upper 20s, while Felicia has gotten more than a little of her damage from adaptive damage.
- Use an atk boon. I run into so many matchups where I'm short by about 2 points of atk.
- Use an atk buff. I'm short by about 2 points of atk when she's receiving hone atk and perhaps Marth's Falchion buff.
- The way IS is making armours nowadays with free doubles on both phases, Felicia is losing some value again for arena. Marteen, who wrote the guide I'm going to share with you, said that things gradually improved for a while, and in the current dragon+armour meta and with the outrage of inflated stats going to entirely new levels I think things are getting worse for her. The reason I say that armours' doubles are making it worse for her is because they can now dump their spd entirely and put all their points in def and res, which will enable them to wall her adaptive damage, or sometimes even atk and just OHKO her back.
- Felicia probably won't ever lose her value as a ploying unit. 35 base res at neutral is one of the highest in the game. In arena, ploys are probably more reliable than smokes because she won't always find a target she can safely initiate on unless she's using windsweep or watersweep, and even then not necessarily because you could run into a team that contains only units from the other side of the spectrum.
- QR is a safe option for when mages get too fast. All she will need to do is block their double and double back. With Plate+eff and the glacies activation, she'll delete pretty much any mage. I've even won against TA+raven mages (this one is not as consistent though) and against W.Tharja, who's problematic because of high mixed bulk. And don't think QR is silly just because she has 37 neutral spd. I've recommended +atk, whereas most mages will go +spd, so even a mage with 35 neutral spd starts faster than her.
- If you support her spd enough (and it probably requires spd ploy combined with at the very least a +4 spd buff), she might be able to rely on natural doubles when not at a merge disadvantage, in which case use desperation. Don't expect to one-round Nino+10 without QR unless you have at least 5-6 merges, spd ploy, and a buff.

Here's the Marteen guide. I'm not entirely convinced about the def-buffing school of Felicia play, but I've seen it work. Marteen did a support solo 0 damage taken on the Seliph & Julia BHB (and she really did wall Seliph's draconic aura without a scratch; it was spectacular), and Nadgey showed her with double fortress def recently, supported by M.Corrin and a def tactic. In Marteen's case I think she just found that IV first, found that she could just QR kill a lot of ranged units, and decided to use Felicia that way. It's an effective interpretation of Felicia, and it actually works somewhat well against the DC meta, but I think I prefer to be less reliant on special activations. But you must choose for yourself; it's not for me to make that decision for you.
https://docs.google.com/document/d/1pUHipAmv09FCn71Shh_Yks89c4YkCoMbmUuegF1A8C4/mobilebasic

Give it a try, make a build, show me, and I'll offer you further tips.