Let's start with the basics.

There are 2 different resources you need to collect to in the end beat the game, those are; scrap and war assets(WA). This strategy builds on the fact that 1 warasset = 1 boss damage while 1 scrap can mean the difference between having a MK1 or a MK5-R weapon.
Therefore I highly recommend taking the missions with the highest scrap reward and pray for as many scrap for WA trades as possible as even losing 60 WA are worth the extra 500 scrap you get from trademissions.
You know whats even better? Trade missions can give you parts plus they wont ( they might? I have yet to come across one) damage your Ironcast so you will make even a bigger gain of scraps in comparison to the other mission types.

Avoid hard difficulty missions and missions where you have to fight more then one Ironcast. The reward for beating extra Ironcasts are slim compared to the risk you take for ending up with a bad board or the enemy Ironcast spawning with weapons you are not equiped to deal with. The same goes for hard difficulty missions, the chanse to get a reward that is greater then the risk of blowing up is not in your favour. This is especially true on the first half of the game.

The Warwick.

Ability to reduce damage✓
Strong starting shield✓
Big ammo capacity✓
Cool name✓
This thing is a beast. Use its innate ability to reduce incoming damage smartly and it will lower the amount of scrap you have to spend repairing by a great number, meaning more scrap to spend on uppgrades and weapons. Its biggest weakness is that it start with only 7 energy and the densshield costs 4 energy.
I recommend to play as Ares Powell and/or as soon as possible spend 1k scrap to get up to 8 energy storage.

I have noticed that the AI usually wont go ham on one kind of defence, they intsead like to split them up, meaning that it will come a time where the AI can't support having bouth shield or/and movement at the same time.
Take advantage of this and use the energy lance to get clean hits when the enemy has low movement and use the light canon or even better its energy based brother to take down fools with no shield.
I hear you saying "It's random chance, you can't depend on getting those weapons before the bosses".
To that i say;" Fear not as you in the worst chase only have to sacrifice some trade missions for a Scavenger mission as those will usually supply you with what you need."

However the chance of getting the right weapons are lower before the first boss as you wont have as much time, making it partially harder than the final boss.

You can pick to enhance 2 different sides; the board or the effectivity of your collected nodes.

A bad board can ruin your game in one single fight and nomather how skillful you are, bad luck still exist.
Getting the abilities to change the type of node can help you escaping from a sticky situations and get you a stockpile of something you might need in the future. Other good ones are the 100% coolant refill and the clear board of a colour one.
If you believe in the board and in your skill in getting a few enhancers for your guns can turn the boss battles from a nightmare to a walk in the park.

Get upgrades that gives double attacks and combine them with the energy balance for high damage per ammo or maybe a EMP and then fill the enemy with holes with the multi-attack weapons.
Avoid the level ups that gives a flat % to eg. the spawn rate of ammo as they aren't game winners. The repair ones are usually not worth it and the hull heal are good at the start but will fall of in the late game, so take them early if you can but dont keep them to long.

What I have noticed from my fights with the bosses(and really all Ironcasts) is that they like to repair the defences and if they can do, deal damage to you. Even if it's just 1 damage the AI will try to attack.
This will help you greatly if you have a shield that can on level 2 absorb 80+% of the bosses missiles (around level 4 normal or 3 dence) and good enough weapons to punch trough the shields and laser/ball-thingy weapons they have.

HERE IS THE IMPORTANT PART! This will keep the enemy in a loop where they will repair the shields/drives and then fire at you dealing about 50 damage with the missiles per turn. With good weapons and abilities you will only take damage on the first round(this is where the Warwick main ability comes in) and then in 2 rounds take down all the enemy sub-systems to 0 health. With bad luck you probably have to take the 50 damage/turn but as you will have over 1k health at this point there won't even be a rush to finnish the battlt for you.

As you can see and hopefully experience, there are many ways to beat this game as long as you have scraps to get the weapons that combo with what you got when you leveled up.
Shields and drives aren't that important on the boss fights but will save you scrap during regular missions

If there is something you didn't understand, somthings lacking or if I got something wrong please don't hesitate to tell me.
Remember, though that this is only one strategy to beat this game and you can still lose to the first boss when the game decides that not giving you any good MK2 or higher weapons would be funny.

GLHF