Software: changes all the time - but usually involves a flux epure 3, uad shadow hills and massive passive - limiters: tough one: I always thought invisible limiter was by far the best, until I used it on a big outboard mastering session on big atc scm 150's and heard how it "digitalised" the sound.
Also since I have my lipinski l70's speakers I really heard how f*cked up software limiters can sound.

Ever since then I prefer outside analogue mastering by my friend Marcel James - usually involving a sontec 432 eq, summit audio, bae audio and Api 2500 (hardware) comps fed into a (hardware) waves l2 and antelope audio pure 2 for a/d clipping - tons of headroom and loudness and still sounds real.

i produced some commercially released songs that had 130+ tracks, as well as songs that only had around 20 tracks.

I don't think there is a "must" of a certain track count, layering /stacking can help up creating a wall of sound, but it also harder to balance sometimes

Start with getting your room right - bass traps etc. An untreated room is your biggest enemy when it comes to judging the bass properly.

Lexicon for pretty much everything, Sonnox Reverb for Drums and Ambience, then there is this plugin called UVI Sparkverb which I just love.

For mobile work, I like the apogee duet 2 - on the affordable end and the sound quality is pretty good.

If you want something that let's u hear more detail, u probably gotta look beyond 2.000 $ interfaces. My main interface is the Antelope Audio Zen, the sound quality is not comparable to "cheaper" interfaces.
However, it still doesn't create a great song by itself 

Geez Matt! You can launch a rocket with this thing!

My alltime favourite is (until this day) the Clavia Nord Lead 3!
Can be aggressive, Fat, (kinda) analogue, sweet - and it looks great. Haven't really tried the newer ones (except a couple of minutes at NAMM last year), so can't judge them.

Also amongst my favs is my beloved Roland JP8080 (JP8000 rack version). A classic of trance, it is famous for it's supersaw, heavily used from the end of 90's onwards... Unfortunately mine is very buggy and needs repairs every now and then - otherwise really awesome.

Another great one I like to recommend is the Dave Smith Prophet 08 - analogue, can sound "heavy", "dirty" and "dreamy" at the same time.

Also used all kinds of Virus models over the years, great allrounders, but I personally prefer the sound characters of the synths above more.

What's your favourite Hardware Synths?

Before even considering Equing a kick make sure your room sounds good (or actually doesnt "sound" at all). Especially Kicks (Bass / Subbass area) can be tricky and kinda falsified when played back in a non-acoustically-treated environment. I've spent ten thousands of $ of gears over the years before even starting to treat my room properly, if you invest a little bit in your room (acoustic panels) it will save you a lot of trouble.