marine + strength + energy + maintenance for a first time player all the way, that extra smash power and a working laspistol make all the difference on the first two decks.
My tip for a first full play through, is go Navy with a mix of weapon skills. Mix hacking skills and weapon.
If you make it through that, go psi on 2nd run. I found psi a good one to go once you fully get how the game works. Mix in hacking skills where needed.
This is just about all the information you should need to help with blind play through. Don't worry about doing every little thing perfectly, and enjoy the game.
I've played it before but didn't finish it, and now I want to try again, but I've forgotten quite a bit about System Shock 2's mechanics. What I could use a refresher on the most are stats/skills, as I don't quite remember what's useful and what isn't. I remember Maintenance is better than Repair, that Strength is good for inventory space & melee, Standard & Heavy Weapons are generally better than Exotic, stuff like that.