Generally, I've found it best to max your main Attack stat (Physique/Aim, Intelligence if using Charge Weapon).
It is generally advised to pick Melee or Ranged and stick to it. Mixing tends to create underpowered characters.
As a Tech Specialist, you will get some function of Intelligence to: Paralyzing Shock Paralysis chance, Damage (Charge Weapon)/Stun chance (Overcharge), Drone Damage, Shield Defense, Accuracy. Most of your specials also factor in Intelligence.
You get 1/2 Physique as bonus damage to Melee attacks. Likewise Aim to Ranged.
I've found Charge Weapon makes it possible to completely ignore Physique until getting to Zheng Shi (for Augment-Weave), but that was before the Janeria fight was added.
Willpower is not required, strictly speaking, although it is the only major source of Lust defense.
I'm still not sure of the primary function of Reflexes. You can avoid some attacks and the Mines on Myrellion with it. Personally, I see training "Stamina" with Ramis as training Willpower, with Reflexes as a nice benefit.
There are two ways to increase stats:
1. Points you get when you level up (13/level). This is enough to keep 2 stats maxed and 1 reasonably high, which what I suspect the devs expected players to do.
2.
Slow Stat Gain.
Stat Gain by Source.
You do not have to spend your level up points immediately. Slow Stat Gain has diminishing returns as you reach the stat cap, but level up points do not. If you want to max your stats, you are best off using Slow Stat gain early and using you level points later. When you should switch to level up depends on how many stats you're raising and with which methods.
For best results, do not put Affinity in a stat you will raise exclusively with level points. It increases the effectiveness of Slow Stat Gain.
Training at the Ten Ton Gym, with Ramis or Mirrin causes Soreness buildup. The fastest real time way to clear Soreness is probably to Rest for 4 hours. In-game, the fastest way to clear it is eating at the Bucking Bronco Saloon (Four hours rest in 25 minutes). I've gone from 3 Physique to 25 in 24 hours this way with Physique Affinity at level 7 (so long as I avoid the random spectator scenes). Augment-Weave doubles Soreness recovery, making the process much more efficient.
Have you visited the class pages on the Wiki recently? The formulas for a lot of the abilities were added.