I'm still a half noob, my post only contains information based on stuff other people wrote.
About races (only talking about F2P races)
I really can't comment on KDF traits since my only KDF character is an Alien. The problem
with KDF race selection is that many races have 2 inherent ground traits which is often
combined with a limited selection on the last 2 traits. If all you want to do is space battle
the best choice is Alien (you can make it look like an Orion or a Klingon, though). Otoh it's
worth mentioning that most KDF races have offensive traits which go very well with tacs if
you ever want to do ground combat (i.e. the Nausicaan Pirate trait is actually only useful if
you're an tac with stealth module).
On my Alien Tac I'm using Accurate, Elusive, Warp Theorist as space traits. Accurate is
a great choice if you want to do PvP because firepower is useless if you can't hit anything
which is very noticeable when fighting enemies that actually move. The price difference
between weapons with 2 and 3 acc modifiers is huge, which might indicate something.
In PvE it's a good choice as well despite all those unmoving targets because accuracy
overflow raises your chance for critical hits.
Elusive seems to be the defensive counterpart to accurate which makes it a very nice
trait to have.
It buffs Warp Core Potential which adds energy to all systems. A slight edge is still an
edge. More Aux still means better heals and certainly won't be wasted in a MVAE or a
Kar'Fi. It also buffs Electro-Plasma Systems which translates into bigger benefits from
Emergency Power to X skills and a faster system power recharge rate which is very
useful if you use Beam Overload or a pure dual cannons build.
Sadly the only races that can use all 3 are Orion and Alien.
For the 4th trait (assuming you go Alien) the choices seem to be Techie, Efficient Captain
and Astrophysicist. Efficient Captain is often called a mandatory trait but it seems it was
nerfed some time ago. Techie buffs hull heals which is nice and hull repair which is not
that useful for an escort. It gives a rather lackluster +10 rating to the skill, so not really
worth it imo. Astrophysicist might seem impressive because in theory it saves you the
biggest amount of skill points. The drawback is that it effect skills that most tacs wouldn't
even bother investing. Might be worth a look if you want to run a Kar'Fi or the MVAE.
All in all I'd get a ground trait for the 4th spot (soldier in my case).