Firstly, welcome along, to the game and these forums 
My current character is a similar build to what you laid out:
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It is quite effective on the battlefield. You’ll need to learn what your spells do, and perhaps practise a little as to how you do them (I have a song/chant that I use and memorised). With Extra Mana 1 you have 6 mana, which means you can get 6 fighters from 0 to full hits in 30 seconds… unless you use some mana for the other spells, or used Swift Casts a bit, or… well, see point 4. And yes, you can use crystal mana for that, but that gets expensive quickly.
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If you are trying to finance yourself, your Crystal Mana is the most expensive resource on the field for a reason. As well as for spells, it’s needed for the large magical rituals (to the tune of 150 Crystal mana several times a day…), so there’s quite a demand for it. Shop around, sell it high, and keep back 2 or 3 nuggets for yourself, for those emergency castings of spells. As for getting money out of folk you’ve healed, well, see point 4
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What healers do in their spare time is either (a) stuff towards being a better healer:
Getting stuff from others (see point 4). There’s an enchantment: House of Chimes, which allows the regeneration of personal mana. This means that you could feasibly spend it all in the morning, stop in Chimes for a meditation and tea, and then cast spells to help out on the Imperial Hospital for a while. Who will always be happy to entertain more healers of whatever stripe, whatever their capabilities. Do not start swapping tales of 'orrible traumatic wounds, you’ll be there all night…
(b) other stuff related to the setting. This leads into my usual piece of advice to new players, which is to have something to do in-game not connected with your skills.
My first character collected heraldry, and learnt every symbol people wear on the field
My second was bucking for the position of Admiral, tried to know every ship captain on the field, and organise them into mass raids. Oh, and argue for the virtue of Prosperity in Dawn.
My third has the hobby of “small children”, and also sells baked goods up and down the field.
All of them collected and recited stories and songs.
Heck, you can start by just asking “where are you from? What’s that like? What happened last year?”, and if you aren’t careful you’ll end up as the Ambassador to somewhere 
- More than fighters and battlemages and priests, the healers fight as part of a group. Maybe a Hall (in Wintermark), maybe a larger battlefield formation, maybe just accompanying their nation. You have to be part of a group (even a group of one), and everyone always wants to have another healer along.
From that, support and assistance and resources can be requested.
Eg, my character, this last year:
“I will need these potions to help with mana efficiency”
“For healing the House and allies in battle? Here’s the cash.”
“And these potions to distribute for emergencies…”
“Talk to X, get them to make some, tell them I said so. Anything else?”
“I’d like some Twilight Pauldrons in the future…”
“We’ll start saving up, you find an artisan, we’ll supply the funds…”
(Mageblood potions, Elixir Vitae, and Twilight Pauldrons for +mana)
Healers tend to end up with many friends. Everyone remembers that time you ran up to them and saved their life with 30 seconds of magic. You may not have much cash, but with a dozen healed warriors eager to buy you drinks and dinner and the like, and a group to supply your larger needs… what were you after the cash for?
Happy to answer extra questions 
Edit: on mana
You start, with the mage skill, with 4 mana a day. With Extra Mana, that’s up to 6 a day. It doesn’t go very far, but in my answer above I touched on a few ways to spell it out/replenish it. You spend it at the rate of 1 per spell, sometimes 2. You can cast many spells as a Swift Cast version (Heal and Purify are different if Swift Cast), for 2 mana. Crystal Mana can be used for a spell up to 2 mana cost.
So you can cast Heal for 1 personal mana
Swift Heal for 2 personal mana
Heal for 1 Crystal Mana (bit of a waste)
Swift Heal for 1 Crystal Mana.
Keeping back a few crystal mana from the marketplace for emergency usage is therefore big and clever…
One by one their comrades vanished through the shimmering portal, back to Anvil. The howling of the Druj from the woods behind grew louder: they’d found their butchered patrol far too quickly. Edric walked steadily backwards, scanning the woods for movement, shield up with arrows already feathering it.
There! figures in the underbrush moving closer!
“Time to go Edric!” the tired voice of Aestan came from behind him. He darted a glance back; 20 foot to the portal, and only their exhausted healer remaining. Edric nodded and turned to dash back, and as he took his first stride, an arrow sped from the bracken to lodge in back of his leg.
He fell, and there was a howl of triumph from behind, and the stamping of orcish boots dashing for him. Edric looked up at Aestan, gritting his teeth against the pain, which prevented him screaming something along the lines of “Go! Save yourself!” Aestan had used all his power earlier, the orcs were closer by the instant and…
Aestan darted forwards and to one knee, his rune-carved stave jabbing into Edrics shoulder, a glowing nugget within his other hand. “By your oaths and mine, I bind your body whole this day!”
A surge of needling heat ran through Edrics body and he surged to his feet and ahead, Aestan scattered a handful of black dust as he spun and darted through the portal, the howls of the orcs behind him far too close, as he fell through, and back to Anvil. Thanks to Aestan, who always kept a Crystal Mana back for an emergency Swift Cast…
Arrows do Impale: does nothing to the shield, does 1 damage if it hits heavy armour, does 1 damage and incapacitates the location if it hits anything else. So to the (unarmoured) back of the leg, it can easily be a killer
Swift Restore Limb: 2 personal mana or 1 Crystal mana, only takes about 3 seconds vocal instead of 30. Restores the location but not the hit point.
And if you lose a leg, you can’t use it. No limping, no kneeling, no hopping… crawling, maybe.