Just finished greenskin crisis on expert ironman for the first time. Think I'll probably try to take on a second crisis with this save as I still haven't fully explored the map or tried any legendary locations.
Found a pretty sweet famed shield.
Drew I'll write up some advice to help you out.
There are two distinct parts of battle brothers, both equally important: the strategic layer and the tactical layer. I'll define strategy as anything which happens off the battle grid and tactics as anything which happens on the battle grid.
Strategic Layer
(1) Choosing Contracts
You can "accept" a contract after negotiating pay and then say "I'll need to think about this" in order to delay taking the contract. You can use this to look at all contracts at a location before choosing, or to leave a contract up which you intend to come back later and accept.
At the beginning of the game you should look for missing items and brigand contracts. Try to avoid monsters early on unless you're very confident; you can't get armor from them and you generally make less money from their loot. Your primary goal at the beginning of the game should be to use contracts (and any roving bands of brigands that you see) to get enough armor to outfit 10-12 bros. If you find a camp early on, you can likely take it out, too; their difficulty scales with time.
(2) Finding Camps
Once you have some basic armor and weapons you want to plot a course through the unexplored wilderness and take on as many camps as you can before returning to civilization. Use mountains to your advantage; during the daytime stepping onto a mountain will reveal a large sight area around you. Once you've got raider gear on most bros, you'll be hunting brigand leaders and fallen heroes: always try to get their armor and weapons.
(3) Wooden Clubs, Daggers, Flails
Wooden clubs do very little damage but they can stun like any other mace. Use this early on to incapacitate dangerous targets or to pry good armor off of enemies.
Armor and weapons drop based on current durability. Dagger's second ability ignores all armor and only damages health. It has reduced hit chance, so usually my strategy early on is: pick one or two enemies whose armor you want, save them until last, and then surround them with daggers.
Flails are very strong early on because many brigand raiders do not wear head gear. The flail's second ability has a 100% chance to hit head, so you if you dual grip (no shield) a flail, you can often one or two shot a brigand raider in mail armor, accomplishing two things: no damage to his armor, and no more brigand!
(4) Choosing Battles / Battle Preparation
Pick battles you are almost sure you can win with acceptable losses and run from the rest (preferably on the world map as fleeing from battles causes a renown hit, but if you scout out a bad battle at an unknown location, don't hesitate to run; better to lose a few renown than die to a fight you have no hope in). Acceptable losses will vary by campaign time. At the beginning of the game if you can trade a bro without much potential for a suit of chain mail, that is an acceptable loss. If you project losing a veteran later in the game, you should at least be getting a guaranteed famed item (from a rumor or a champion), but even then I would mark the location in my head and come back when you think you can win without RNG (this you mostly have to learn by trying different enemies and either winning or dying, but be conservative if you're on ironman).
Change your load-out based on the enemy composition. For example:
If you're fighting a camp of brigands with many archers on a hill, put kite shields on your front bros, leave behind bros vulnerable to OHKO from x-bows behind.
If you're fighting alps, leave behind archers and low resolve bros, bring nets and maces to stun or 2h axes to OHKO them.
If you're fighting an orc camp w/ berserkers and warriors, bring hammers, axes and an archer bro.
These will all change based on what bros and gear you have available, but you shouldn't feel stuck to a specific gear set or lineup of bros. Say you have four 2h bros in your party, one each of mace, sword, axe and hammer. If you're fighting a small band of orc warriors, it is not a bad idea to swap out the sword for a hammer even if they are not specialized in it. Always pick a load out that will give you the advantage. If you're fighting weidergangers, swap in some cleavers to decapitate; even if your bros aren't specialized in cleavers (though having at least one cleaver bro is a good idea) the extra decapitates on low health targets will swing the tide of battle in your favor. If you're fighting skeletons, don't be afraid to slap polemaces on all your backline bros; blunt damage will often one shot them.
(5) Expendable Bros
If you recruit a bro without much potential (usually meaning low m.atk), give him fast adaptation, backstabber, & a wooden club and just have him spam stuns on people. If he dies, it's not a big loss, and with those two perks he will be able to land some stuns. If you recruit a decent shield bro but you've already got two bros with great potential to be shield bros, give him a shield and put him in dangerous situations before your more valuable units--if he dies, no big deal and you can invest in the future of your higher potential bros. Especially early game, always try to make the best out of every recruit; don't give up anyone's life without an acceptable return (like a suit of armor or to save a more promising bro's life).
(6) Buying / Selling
Generally buy in small towns and sell in big cities. I tend to keep a round shield on me to see what the buying price is. Base price for a round shield is 15 gold. If it is selling for 20-22+ that is good for making money. I wouldn't sell treasure (goblets, chalices, etc.) when buying price for a round shield is less than 18; treasure has a higher price:value ratio. Sell cheap loot at any town instead of waiting for a big city if you're going to run out of pack space. Cities will pay more for your goods depending on your relationship with them. It's good to build a relationship with 1 big city and a small or medium town with a workshop (you'll see it on the map) to buy tools at. Certain city events make selling prices better, like ambushed trade routes. Be careful of completing certain contracts if you want to sell your stuff as clearing out bandits or lindwurms can remove ambushed trade routes condition.
(7) Repairing High Value Items
General rule of thumb, if the value of an item (when you mouse over it in your pack) is 10x the
current durability it's worth repairing before you sell it (if you can buy enough tools to repair the gear you're using). Meaning you'll make more gold selling it than the price of the tools you used to repair it.
(8) Famed Items
Use tavern rumors to locate famed items.
Taking a 1 or 2 skull contract to clear a camp will make it impossible for a famed item to spawn at that camp. A 3 skull contract can still spawn famed items. I generally negotiate 1 or 2 skull camp contracts, see what the heading is, and then go clear the camp myself without the contract. Doing so will usually net enough money from selling loot to make it worth it anyway and you can spawn a famed item. The exceptions are if I want to build relation with that city and the camp is close to town (camps that are farther away from civilization have higher chances of spawning famed items).
Tactical Layer
(1) Surround Bonus
If two of your guys are next to an enemy, all melee attacks against that enemy get +5% to hit (this is true for reach weapons, too). This bonus increases by +5% for each of your bros above 2 around the enemy. Early on, your best bet of getting good gear without buying it from the shops is to surround a bandit leader or fallen hero with bros and use daggers to puncture him to death without damaging his armor.
(2) Breaking Morale
Against humans and greenskins, breaking morale is one of the best ways to win fights. Doing HP damage (over 15 w/o fearless perk) causes a morale check, as does putting more than one bro next to an enemy. This means that if you have a bro with 3 AP left, he can't move and attack, but if he moves next to an enemy who has another bro by him, it will cause a morale check for that enemy. You can actually break multiple people in one turn simply by walking along next to them. Broken enemies also do not have zones of control, so you can just walk passed them. Once you break an enemy, they are generally out of the fight and you can ignore them; try to kill them with attacks of opportunity and focus your fire on non-broken enemies. Sometimes waiting until after they try to flee essentially gets you two turns in one. There are two exceptions to this: First, if the opponent has someone who can rally or if you think there is a good chance the opponent will rally themselves (e.g. if they can likely kill someone by rallying), you can try to actively finish them off. Second, if there are enemies who are likely going to do a lot of damage to you before the broken enemy flees, you can try to actively kill the fleeing enemy (esp. with a decapitate or other fatality) in order to break other enemies.
I hope that helps. If you have any specific questions, feel free to ask.