Send the runners for malachite ore and diamonds to sell in order to build up gold. The ore runner is your best source of gold, and should be upgraded first, after which upgrade the herb runner if you need potions, or the gem runner if you don't (to concentrate on gold first).
To fully upgrade all of them it will cost 42,000 gold (1k + 2k + 4k for the 3 levels of upgrades, for both weapons and armour, for each of the 3 runners. If they are hurt, which doesn't happen too often when they are upgraded, it costs 100 gold to heal them (by talking to your alchemist).
In a test sending the runners out 7 times before upgrading them, they came back successful twice, but then averaged 2 hurt each time they returned (all 3 hurt once, 2 hurt 3 times and 1 hurt once), for a success rate of 52.4%. Sending them out 7 times fully equipped, each of them was hurt only once, for a success rate of 85.7%.
Of the successful returns for each of the runners, when unequipped (vs fully equipped) they brought back, on average, 2.5 (10.8) ginseng, 3.7 (9.8) malachite ore and 3.5 (11.5) diamonds. The average over all trips, successful or not, when unequipped (vs fully equipped) was 1.4 (9.3) ginseng, 1.6 (8.4) malachite ore and 2 (9.9) diamonds.
The average cost to heal runners (at 100 gold each) per trip, was 143 gold when unequipped and 43 when fully equipped (1000 gold total unequipped, vs 300 when equipped).
Other than getting a 'perfect' quality item for each creature part, I don't know if there is much to suggest. There isn't any benefit to getting all parts from the same type of creature. Actually, aside from one ghoulish torso, most of the torsos I kept were from an unlisted source.
At the end of the game I had a perfect dragon elf head (level 10 Magic Missile / Magic Blast), perfect torso (+105% to all armour ratings), perfect goblin arms (+110% HP, +110% melee/magic damage) and perfect dragon elf legs (+100% CB/HR/IW). The perfect mage head I actually found pretty late, and had been using a level 8 (well preserved, I think) mage head for quite awhile before that.
There are minor variations on creature parts that can give you a little extra on one value, at the expense of the others, but I never noticed a particular vulnerability, so kept the armour rating, and CB/HR/IW even. Early in the game I used arms focusing on HP bonuses, but as damage bonuses started to become reasonable large, I went with more balanced arms that included both. I didn't notice a difference with less hit points (as long as the creature can last though most of a tough fight, it is easy enough to re-summon it if it gets badly hurt or killed).
I didn't notice any problems with my creature getting involved as a mage (but then late in the game he was used more as a distraction than help, so I didn't keep track of him a lot). Earlier in the game, I did notice he wasn't very aggressive with a warrior head when I was using a bow to start combat from a distance (either to start doing damage first, or to try to bring opponents to me). Doing parts of the fjords before getting the battle tower, he seemed much more aggressive with a ranger head (even wandering around and attacking opponents a little out of my range a couple times while I was healing or waiting for my mana to refill before proceeding).
walkthroughguide (with screenshots)
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