I always wanted to do this, here is what I have chosen:
I found that I don’t need any of the more advanced Combat skills and could not afford any of the Support ones. I also tried to pick only “realistic” skills, ones that make sense in a learning sense. Did not always work out though, the greed set in for more ammo at some point. 
I am on PC.
1st toon:
2nd toon:
I ended up rather combat heavy, but I like the combination of Sharpshooter and Vanguard for different scenarios.
Toon1 uses PVG, AI-76 and Magnus - rather noisy weapons.
Toon2 uses silenced rifle, SMG and Klaucke - more stealthy. T2 is also immune to ticks, as per Tene’s vanguard video. 
That is actually tempting!
That’s what I thought as well… If I remember correctly, it’s the combination of Stand your ground, T2 Armor and Vanguard. Tene goes through it here:
Are you on PC or console?
And the immunity does not work for explosive ticks, right?
On PC. And no, not for explosives, only normal tick damage - which is annoying enough!
I don’t think you’re immune to ticks anymore. I’m not, but I used to be :-p
Hmm gotta check that next time I run into some of them that are not radioactive ! 
And if not - it was good while it lasted! 
I have 4x chars, ordered by from the oldest to newest (playing on PC):
All weapons between chars have same mods;
.50 cal - 5* mag, 5* 8-16x scope, IR/OPV vision
AG4 - 5* barrel, 5* mag, 4-8x scope, IR/OPV vision
m/49 - none
HP5 - 5* barrel, 5* mag, 5* Red dot
Kpist - 5* barrel, 5* mag, 5* Red dot
Glock - 5* silencer, 5* mag
Magnum - 5* silencer, 5* 2-4x scope, IR/OPV vision
Here’s mine! I can say for sure I would LOVE to have TECH based builds join my game!
I’ve yet to see someone using the TICKS skill, that would be awesome!
This is my only character besides a level 2 permadeath I’ve started. That one isn’t old enough to count.
I thought the level cap was 41 while I was building it and didn’t find out otherwise until I was 29.
My priority was survival, leathality (as a subclass of survival), and teamplay. My idea of survival is not getting killed, and killing other things quickly, so I went for damage reduction for me, and bonus damage for machines where I could. I thoguht I could work towards marksman which is the main reason I put skills in the left tree. I didn’t realise I put nothing into stealth.
Co-op came late for me. I built most of this for solo play, but then showed the game to two friends who bought it. I like support roles with a spicey DPS edge in team play, but I found that the way people play this game the healing skills didn’t seem that useful. I use a lot of flares and either utilities for support, and pop up at the last minute to explode things instead. It gets the job done.
If I built it over again, I’m not sure what I’d do differently.
Can confirm that sadly tick immunity is gone and so is the gas immunity, it was really nice while they were around but i guess they can’t have us be running around in gas rooms and having ticks jump on our heads without any worries. 
Hey, your Engineer is basically my build! I always wondered what to call it.
Only I use a 1-4x with thee AG4. Need to be ready for close range.
Borg? Sounds Swedish…
Now I’m a little more ok with my K/D.
You have a spare skill point and it’s not in the health boost skill. 
Going for learnable skills is a really nice idea, I like that. I’d argue though that it’s not so much a skill tree as it is an experience tree. We do a lot of running around Östertörn, it would do wonders for our stamina. Similarly given everything we put up with, I think our toughness would improve a little as well, or at least our attitude to it. That’s how I see the health boost ‘skill’ + being able to handle a knock and keep going. The same applying to learning to manage recoil or not get knocked down. Then again, I can also look at the health bar as a ‘luck meter’ for the times the bullets just missed. Sooner or later my luck runs out.
First I went for running speed / storage capacity, and then focused on that path to unlock the “survivor” perk, and along the way grabbed lock picking, and improved aim.
I hadn’t realised that the level cap kicked in at 31, so I thought I had a few levels to go. It was all pretty organic and not planned out, but it suits my play-style.
Looking back, I might have planned it a little different. My alts are all only around lvl 6 - 10 but the first few levels I’ve pretty much gone for the same first few.
A lot can be explained with physical training and experience, e.g. in aiming. Both is fine for my interpretation of ‘learning’ (the body learns, too). Some of the combat skills would have been fine. But I needed the other ones as I felt I could do with my own physical combat (mouse) skills and the guns I find. I had trouble justifying growing iron skin and the like.
Yeah, I’m still undecided about that one. The tick specialization? Not sure if that is not too much fuzz for little benefit. Also I am basically done with the game. I started the DLC, but so far it has not really got me hooked.
I was running around with 11 skill points unspent for a while as I was already doing fine. At some point I grew tired of fighting, though, and bought some skills I could not really justify with my learning interpretation of skills. High standards out the window.
This is my main.
Has Marksman for sniping and Vanguard for running about and more hands-on encounters. Also had ticks immunity (which still seems to work on milticks sometimes, but no longer all the time, never did on FNIX splodeys, nor on the Apo scorpions).
3 points left over (in line with my assertion that most things beyond level 20 are “nice to have, but not critical”) as there isn’t anything I desperately want. If I played co-op more often, I might go for enemy marking, it’s a neat little quality of life thing.
So judging by the above, pretty cookie cutter.
This is my original character (all the way back from beta).
Not too different though, except that she has tech all the way up to hacker, which in retrospect I consider a complete waste. She has some additional quality of life stuff like the aforementioned marking, but in the end, nothing that particularly matters. If anything, she misses Steady Feet.
In other words, the level 60 character from beta played largely like my level 30 character from the released game does now, informing my view that people saying “but if you removed the level cap, the game would become terribly unbalanced” very possibly don’t know what they’re talking about.
Here’s my second character. This time around, I wanted to focus a bit more on support for coop games.
I got both Marksman and Vanguard unlocked. For long range sniping I switch to Marksman, otherwise I mostly stay in Vanguard mode.
The support skills are Flanking (this skill may very well be the best skill in the game during coop!) and Enemy marking in combination with Designated target; 30 seconds with a 10% damage bonus from everyone is pretty sweet, and you can mark a bunch of targets at once.
As you can see I got one more level to go - your suggestions where to put that last point then? 
Since your char is combat focused, i’d put the last one into Reload Speed. Stamina Amount would also be a good choice if you want to sprint for longer.
