Dispel Magic for the extra 3rd slot.
Go to Bard 4
Learn Medium Armour Mastery
Learn Shatter
Replace Detect Thoughts with See Invisibility
Cantrip to follow. What books can I select from, other than the PHB and XGE?
Bitur’s is complicated. @Hoopy_Frood
You get 2 more infusions known and 1 more infused item.
You also get 1 more spell memorized.
You become an Expert in all your Tools, just in time to improve your Compound Bow and use this infernal Machine to track Saruman. BTW: you could probably rebuild your steel defender incorporating the Machine. You are an Int base Caster. … Think it over.
The few Acquisition Incorporated Bard Spells look fine. What other books add Bard Spells?
I’ll add Thunderous Smite (level 1 paladin spell) to Ceol’s standard suite of memorized spells.
There are spells in the Sword Coast Adventurer’s Guide, but none for Bards. Booming Blade is good against enemies who move a lot, and Green-Flame Blade allows damage to be dealt to two opponents.
I’m hoping there will be some stuff in Tasha’s Cauldron of Everything, which (iirc) comes out next month. I have it on pre-order.
I like those 2 spells, but as you said, not for Bards.
Possible Feats for the Fighters: @Elendil_s_Heir
Thoroncir, if you want to commit even more to being the mounted knight
Mounted Combatant: If you’re mounted, get advantage vs unmounted foes.
Force any attack on your mount against you instead
If mount makes a dex save, takes no dam instead of half and half on a fail
To really ensure you mostly go 1st in combat:
Alert: +5 Initiative & can’t be surprised if conscious & sneak attacks don’t gain advantage on you.
Blade Mastery: +1 to hit Swords, Can use reaction to parry for +1 AC until start of next turn; Opportunity attacks get advantage.
Fighting Initiate: pick an additional but different Fighting Style, for example Dueling gives a +2 dam with 1 hand melee weapons, Rest of list here
Mobile: +10’ speed, Can Dash over Difficult terrain no penalty & don’t provoke Opportunity attacks.
Skilled: Pick up 3 skills or Tools. (This is very nice if you like skills)
Many of these might be of Interest for Gwaelur also. @NAF1138
For Dwarves & Small races only:
Squat Nimbleness: +1 Dex or Str (max of 20), +5’ movement, gain Acrobatics or Athletics skill & Advantage to break Grappled.
Fell Handed: +1 to hit Axes & Hammers, If have Advantage in Melee knock target prone if both d20s would have hit; If you have Disadvantage and miss but the higher d20 would have hit do 5 points damage anyway. You can use a Help Action to knock an opponents shield aside for an ally and give ally advantage. (at least a +2 to hit for the shield)
The is also Lucky: 3 luck points per Long Rest. You can choose to reroll the d20 for a save, skill or attack.
Of course look over the list, just some suggestions.
Other feats to consider, just from the PHB.
Alert: +5 to initiative; cannot be surprised while conscious; creatures hidden from you don’t get advantage to attack you.
Heavy Armour Master. +1 to Str (max 20); Bludgeoning, Piercing and Slashing damage from non-magical weapons is reduced by 3.
Resilient. Choose an ability. Raise that ability by 1 (max 20). You gain proficincy on saves with that ability.
Sentinel. The speed of creatures you hit with an opportunity attack drops to zero; Disengage action does not prevent you from making opportunity attack; creatures within 5’ of you who attack another target who does not have Sectinel feat trigger opportunity attack from you.
Tough. Increase hp max by 2 per character level. This also applies when going up levels in future.
Others worth considering include Crossbow Expert (if you use crossbows) Observant, and Polearm Master (in combination with Sentinel).
You can gain spells with Magical Initiate (two cantrips plus a first level spell or Battle Master maneuvers with Martial Initiate.
Thanks for explaining how Ghan will work @ 6th level.
Please do update my character (and I’m happy for everyone to see it.)
(Honestly I have tried to follow the Internet explanations of spells slots. ‘knowing’ spells, preparing spells, casting spells, spell devices and cantrips.
Sadly it’s not really gone in to my elderly brain. 
So if you select any additional spells for Ghan, I’ll do my best to cast them. 
)
P.S. Anyone who wants the +1 Bow can have it as far as Ghan is concerned. 
(We’re a party - make use of everything…)
I was considering crossbow master as my next feat actually. Balance out my character a bit and help the party by giving a little bit of a ranged attack. Also, iirc, crossbow master makes my crossbow useful at close range as well. Gwaelur showbe great with all his weapons.
I had read a lot also about how Sentinel was an awesome feat too.
Those are both good choices. There is a lot of love for Sentinel among players I know.
The Crossbow Expert I think overall though it is a small help to your character. If a creature is within 5’ of you, You want to split them with your Great Axe. If you’re using a 1 handed Axe, Better the shield in your other hand than a Hand Crossbow.
One of the most classic Dwarf builds is Great Weapon Master, Sentinel and the Tunnel Fighter fighting style. You become the ultimate is close quarter combat. I would allow swapping Dueling : +2 Dam if 1 handed for Tunnel Fighter.
As a bonus action, you can enter a defensive stance that lasts until the start of your next turn. While in your defensive stance, you can make opportunity attacks without using your reaction, and you can use your reaction to make a melee attack against a creature that moves more than 5 feet while within your reach.
Oh, I like that. OK let’s go that way.
@MHaye, what do you suggest for Ghan’s extra spell?
Without knowing exactly what he already has, I minght miss a trick or two.
Wind Wall looks like a good defensive spell, especially if we run into someon with a fondness for Cloudkill. It would also render missile weapons useless (except for siege engines or giant-thrown rocks).
If we come up against crossing a liquid (or even if we go on an excursion to somewhere with a lot of snow) Water Walk is an idea. It’s a ritual, so it can be cast without expending spell slots given enough time to prepare. Similarly, Water Breathing would be useful to explore the bottom of a lake.
These last two can be switched in and out with a day’s warning.
If he wants an aggressive spell, and does not already have Call Lightning, that’s worth thinking about.
Next level, I’d go straight for Conjure Minor Elementals to make use of his Mighty Summoner feature, but that’s for the future.
Sorry, current 3rds: Conjure Animals© 1hr; Plant Growth; Water Breathing® 24hrs
I like Call Lightning, but I think @glee is trying to play Ghan as a support character. Wind Wall© 1min 120’rg 50’x15’x1’ is interesting. Maybe Speak with Plants also.
Ghan has:
Cantrip: Druidcraft, Mending, Poison Spray
1st: Cure, Goodberry, Entangle, Faerie Fire
2nd: Lesser Restore; Healing Spirit, Spike Growth
3rd: Conjure Animals, Plant Growth, Water Breathing
I have Wall of Thorns (and a lot of useful but inoffensive spells) on a Rod.
I like the sound of Call Lightning. 
Ghan does like supporting - with just an occasional Blatt!
(and I already have Speak with Plants on my Rod…)
Artillery can be considered as support…
@glee - what is your Wisdom? You can prepare Druid level + Wis modifier spells, so what you have prepared looks like a 5th level Druid with 18 - 19 Wis. Is that right?
I just added Call Lightning so new list: 11 spells as 6th level +5 for Wis 20.
1: Cure Wounds d8+5; Goodberry 10 berries; Entangle © 90’ 20’sq str dc; Faerie Fire © 1min 60’ gives adv. to hit. Cancels invisibility/stealth
2: Lesser Restore (T) ; Healing Spirit © 1min d6/t 60’; Spike Growth © 10min 150’ 20’r;
3: Conjure Animals © 1hr; Plant Growth; Water Breathing ® 24hrs; Call Lightning © 120’ 10min 60’r x10’ use action for 3d10 Dex 5’r