Formidable:
Since the Scorch rework this has been Fernando's go to Legendary. (Yes I call them Legendary cards, not talents, I'm an older player)
This grants massive self sustain and will easily save you from death when coupled with your shield to cleanse cauterise.
It has a 45 seconds internal cool down though so don't let it change how you really play or think too much.
Incinerate:
A considerable chunk of Fernando's damage comes from his Fireball, as it can pass through enemies; suffers no damage fall off; and has some serious range to it.
This decreases the cool down by 50% allowing you to spam it twice as often. You'll often get to use it 3-4 times in a duel before being forced to play defensive, if it ever comes to it that is.
Cavalier:
This card can work at literally any level depending on how you wish to prioritise your cards.
I personally prefer having it at level 3 and above, as this puts Fernando at 5,000+ health whilst not eating up all the loadout points.

Formidable
Charge
You now have 2 charges of Charge, each Charge deals an additional 100 damage, and you are Immune to Crowd Control while Charging, but the Cooldown of Charge is increased to 13s.
Level 1

Incinerate
Fireball
Reduce the Cooldown of Fireball by 2.25s.
Level 5

Cavalier
Armor
Increase your maximum Health by 450.
Level 3
Brand: [Still in testing.]
Theoretically the poke of 4-5 hundred healing will allow you to sustain in duels easier, effectively a 'safer' aggressive style.
Hot Pursuit:
This loadout card is effectively mandatory for a particularly aggressive or Flanknando style of play, as the 40% increase in speed allows for easy chasing, quick retreating, or other such simple re-positioning.
Due to the cards internal cool down of 10 seconds, you're most likely going to proc this speed buff every third or so Fireball. (Assuming you're spamming as soon as possible and never missing)
Immovable Object:
This card is most ideal at level 4 or 5, but can be used at lower levels as a filler if need be.
This card is best for styles that involve remaining in your healer's healing range, or that involve a more cautious approach due to high damage output from the enemies.
If you can block the enemy team's damage for 1.5 seconds with your shield, this card allows your team's healer to very quickly heal you back up if you're below 50%.

Brand
Fireball
Heal for 500 for each enemy hit with Fireball.
Level 5

Hot Pursuit
Fireball
Increase your Movement Speed by 40% for 3s after hitting an enemy with Fireball.
Level 5

Immovable Object
Armor
Increase your Healing received from others by 20% while at or below 50% Health.
Level 4
Last Stand:
It's just a little bit of self sustain to help you when your in a pinch.
It has no internal cool down and as such can be used whenever, though it is entirely shield dependant, rendering it almost useless in the face of strong wrecker.
Heat Transfer:
There's never any need to have this card above level 2.
At level 1 it allows you to reduce your Charge's cool down by up to 4 seconds. This won't let you spam the ability, but it'll certainly reduce it enough to increase your chances of having Charge off cool down in time to escape.
Launch:
It's just a comfortable increase in the distance Charge can go.
Useful for easier chasing and escaping, less useful if you prefer Charge for just short, yet quick, re-positioning.
Safe Travel:
Safe Travel requires a couple more points to be as effective as the other filler cards, but it's usefulness is undeniable.
It allows for a slightly safer initiation with Charge, and then allows you a margin more room for error in your Charge's use for escape.

Last Stand
Shield
Heal for 90 every 1s while Shield is active and you are at or below 35% Health.
Level 1

Heat Transfer
Shield
Reduce the Cooldown of Charge by 0.5s for every 1000 damage your Shield takes.
Level 1

Launch
Charge
Increase the travel distance of Charge by 15%.
Level 1

Safe Travel
Charge
Gain a 150-Health Shield for 3s after you use Charge.
Level 1

Hot Pursuit
Fireball
Increase your Movement Speed by 40% for 3s after hitting an enemy with Fireball.
Level 5

Incinerate
Fireball
Reduce the Cooldown of Fireball by 2.25s.
Level 5

Cavalier
Armor
Increase your maximum Health by 450.
Level 3

Last Stand
Shield
Heal for 90 every 1s while Shield is active and you are at or below 35% Health.
Level 1

Launch
Charge
Increase the travel distance of Charge by 15%.
Level 1

Formidable
Charge
You now have 2 charges of Charge, each Charge deals an additional 100 damage, and you are Immune to Crowd Control while Charging, but the Cooldown of Charge is increased to 13s.
Level 5

Immovable Object
Armor
Increase your Healing received from others by 25% while at or below 50% Health.
Level 5

Incinerate
Fireball
Reduce the Cooldown of Fireball by 2.25s.
Level 5

Cavalier
Armor
Increase your maximum Health by 450.
Level 3

Last Stand
Shield
Heal for 90 every 1s while Shield is active and you are at or below 35% Health.
Level 1

Heat Transfer
Shield
Reduce the Cooldown of Charge by 0.5s for every 1000 damage your Shield takes.
Level 1

Formidable
Charge
You now have 2 charges of Charge, each Charge deals an additional 100 damage, and you are Immune to Crowd Control while Charging, but the Cooldown of Charge is increased to 13s.
Level 5

Cavalier
Armor
Increase your maximum Health by 750.
Level 5

Incinerate
Fireball
Reduce the Cooldown of Fireball by 1.8s.
Level 4

Immovable Object
Armor
Increase your Healing received from others by 20% while at or below 50% Health.
Level 4

Last Stand
Shield
Heal for 90 every 1s while Shield is active and you are at or below 35% Health.
Level 1

Heat Transfer
Shield
Reduce the Cooldown of Charge by 0.5s for every 1000 damage your Shield takes.
Level 1

Formidable
Charge
You now have 2 charges of Charge, each Charge deals an additional 100 damage, and you are Immune to Crowd Control while Charging, but the Cooldown of Charge is increased to 13s.
Level 5
This is just my personal loadout I use for when I'm a solo tank, it has more emphasis on survivability over damage or aggression due to the likelihood of my having to contest the objective more often.
(I would advise against solo tank Fernando honestly, due to there being some far better options for solo tanking such as Ash and Inara)
Cauterise:
This is Fernando's best item.
His flamethrower allows you to effortlessly cover an entire area in cauterise afflicting flames, and since the damage over time affect can also apply cauterise, you're able to extend it's duration by a further 2 seconds.
Do not get any other items before this has been maxed out.
If need be a second item can be purchased once this has reached level 2.
Rejuvenate:
Due to gow big of a target

Level 3

Rejuvenate
Armor
Receive 30% more Healing from other players.
Level 3

Master Riding
Armor
Increase your Mount Speed by 15%.
Level 1

Haven
Armor
Reduce the Damage you take from Direct and Area of Effect attacks by 12%.
Level 2

Guardian
Armor
Increase the effectiveness of Shields you create by 20%. This does not affect most cards and passives.
Level 2

Morale Boost
Armor
Increase your Ultimate charge rate by 30%.
Level 3

Nimble
Armor
Gain 21% Movement Speed.
Level 3

Kill to Heal
Armor
Getting a kill or elimination heals you for 600 Health, unaffected by Anti-Healing.
Level 3
Resilience:
Only get this if your getting hit by lots of CC (Obviously)
Typically a 2nd or 3rd item.
Illuminate:
Only get this if the enemy team has a seriously aggressive Skye that either won't leave your support alone, or is foolish enough to keep getting real close to you.
Typically a 2nd or 3rd item.
Wrecker:
Due to Fernando's damage being comprised of lots of smaller ticks rather than big chunks, wrecker isn't his best item. Only get this if the enemy Torvold is spamming his bubble shield onto his teammates.
Typically a 3rd or 4th item.
Bulldozer:
This should only be considered if the enemy team is running some combination of Ying, Grohk, Barik and Inara. Where your team lacks any form of blaster capable of carpet bombing, whilst at the same time not buying bulldozer to compensate.
Typically a 3rd or 4th item.

Resilience
Armor
Reduce the duration and effectiveness of Crowd Control and Slows by 75%.
Level 3

Illuminate
Armor
Increase the range at which you see nearby stealthed targets by 45 units.
Level 3

Wrecker
Weapon
Your weapon attacks deal 90% increased Damage to Shields.
Level 3

Bulldozer
Weapon
Your weapon shots deal 75% increased damage to Deployables, Pets, and Illusions.