I am wrapping up my Troubleshooter-playthrough and am considering if this breakage of my traditional NO WEEABOO ALLOWED-rules should result in me playing this in the last couple of vacation days.
What's your basic newbie package here? What do I need to be aware off before venturing forth?
This little guide is useful enough to cover the barest basics:
https://elminage-gothic.fandom.com/wiki/Inventory_Management
It mentions the Underground Goblin Map, which I'd recommend you get as soon as you can. Random number of uses instead of unlimited, but it can be cheaply repaired. You can do that or cheat in order to activate unlimited map uses (depending on how comfortable you are with that, rushing the Goblin Map is a bit metagamey, FWIW). Unlimited map uses are not obligatory (and some people would argue it makes for a diluted experience), but the point is ultimately to have fun, so it's up to you.
I wouldn't call the first dungeon well-designed, but it seems to be more of a filter than anything. I'd recommend enduring past it, as the game gets better. The Tree dungeon is the first 'serious' dungeon, but the game arguably doesn't really kick into gear until the Igdra Underground Church. The post-game is the real meat, however (especially Ibag Tower).
Party-wise, multi-classing is very powerful, as it was in so many of the old Wizardry games. Collecting spellsets is useful. For example, a Lord naturally has access to Cleric spells, so creating him as an Alchemist before multiclassing and settling into Lord is a nifty trick (though he'll only have 3 spells from each rank from the previous class). Humans are great for multiclassing, for obvious reasons.
The Wizard spell Diomente is a teleport spell, and very useful. It's one of the last spells learned by Wizards, but it's a good idea to rush it early on. Though later areas in the game have anti-teleport areas (along other nasty tricks).
It's a good idea to have an Alchemist and a Bishop at all times, despite any apparent immediate drawbacks. Researching the EX Skills is also rewarding, some of them are strong like Magic Essence, which causes spells to ignore magic resistance.
Summoners are fun and can make dealing with the difficulty curve easier, as you can capture/form pacts with strong monsters that can join your party and carry you for entire chunks of the game. Their mechanics are a bit involved, but it's worth looking into it.