Well for the main character and your first slave I think it's more efficient to start off as casters no matter how you plan to build your characters, even if it means you have to use a respec potion to redo it later. When you first start off, the ability to heal is pretty much non negotiable and you also really need the ability to open locks, both of which are wits based. Max wits also gives you an xp bonus.
So no matter what my plan is I always give both my main and my first slave max wits, max magic, and apprentice to start off. I side with the mage guild for the free staff and health/mana crystals. If I can get a second staff either by buying one from the shop or a lucky mage quest reward then I do that, otherwise I trade the staff back and forth between those first two characters for healing once they level up. My 2nd class for both is always Acolyte for the healing.
Starting off with wits and mind blast means you can usually manage to open locks on the goblin lair without the thief class but not always. Same with the bandit cave. I usually will grab thief on my 1st slave as my second level up to guarantee lock opening ability. After that it's pretty much always archer and then ranger.
Depending on RNG, sometimes I have to buy a few extra health crystals to get through the goblin lair before I have anyone who can cast heal, but mind blast is pretty good about 1 shotting everything except the boss for anyone with a staff.
I prefer having max'd charm on my protag (to make social skills more efficient. You start with them no matter what, might as well get use out of em.) Which kind of closes off being a mage. First slave is always a mage, and yes I'll make a point to pick up thief on her.
Having to train two separate stats does slow down the early game a little bit, but I am usually able to cludge up enough gear and stats to clear out dungeons by mid-week 2.
Goblins have such low health that you can probably one shot them regardless- assuming you actually have a weapon that isn't total garbage.
Usually, I'll breed my first slave asap. If the resulting child is a dark elf (which is the race I pick for the first slave) with good caster stats than I'll use them as a second caster. Bad caster stats means I sac them to improve one of my other "keepers".
If the child is a seraph with high phys and wits, I keep them for melee warriors. Otherwise, they get sac'd. It's a more reliable way of maxing out your stats- but it's worth running bandits early on because sometimes you get lucky. Go ahead and breed daisy asap as well.
And for those that didn't know- you don't need to wait for them to finish "training" to sac them. You can do it the same day they are born. Obviously, you should choose "no training" to save on gold if you plan to sacrifice them.
I don't rely on heal much, at least not enough to need two people able to use it- lots of fight will drop crystals and if you play your cards right you won't need any while killing goblins anyway. In truth though, with a little luck you can basically just skip gobs and go straight to bandits.
If things get really bad- for instance, you simply don't manage to get enough health crystals or have heal- you can pass time even in a dungeon to heal, or simply go to town without leaving the dungeon to get items. This is far from ideal, but it's better than "dying" and being taken out of action for about a week.
If you aren't familiar with what to offer to what shrines- I'd recommend looking it up on the wiki. It doesn't matter much mid to late game, but early game it's an easy source for crystals and the offerings are dirt cheap.
Usually, by the time I'm mayor, I'll have two or three combat spec'd characters with max (relevant) stats and two or three menial slaves used to do busy work or raise cash. I pick up knight and Valkyrie usually the same day I take the fighters guild lich hunting quest, which makes killing the lich a lot easier. Within a week of becoming mayor I've usually got enough to kitbash full sets of mithril tier gear- at which point you can basically do all the content in the game, although you might want to take some time to fill out your ranks.
Kitting out in adamant, in comparison, takes a *lot* longer, and is rather tedious. Having three strong melee with holy lance makes it a lot easier though- and if you pick up rogue you can get water slash without a skillpoint cost for dealing with Salamanders and Cenotaphs- although the best answer to Cenotaphs (do to sheer defense) is probably lightning orb until you can stack armor pen.