I've got a squat rack/bench press/pull-up bar combo unit,

>>42870185
You probably forget to mention your barbell. If you got one you're set in principle, getting some dumbbells wouldn't hurt probably, also some kind of device to be able to do weighted pull ups, and some (improvised) pads so you don't damage your floor when deadlifting. That's more or less what I got and I'm some kind of sick muscle freak.

It's fine for minimalist training, but that kind of sucks for achieving maximal possible results, but you'll still look better than 99% of the population.

>>42870211
Apart from that this guy >>42870206
mentioned, what is he missing?

>>42870185
the only thing I can think of that you couldn't accomplish with a barbell that has not already been mentioned in this thread is stuff like lateral raises, face pulls, rear delt flyes, etc.

get some DBs and resistance bands of various strengths and you should be mostly set, resistance bands are a good way to replace a lot of the functions of a cable station (you can do face pulls with them, you can do tricep pushdowns with them)

get some dumbells la

Adjustable dumbbells and you have literally everything you could need for a homegym.

>>42870206
>>42870223
dumbbells would probably be useful but not that important.
for the past 1 1/2 year I've been actually making the best of the shitty equipment I had.
I started with a bench w/ stands, a bar, and plates.
Eventually I got a half rack, and a second bar (standard 28mm barbells so pretty cheap, they're only rated for 200kg but that's okay since I never test maxes) that I use to mimic a trap bar (I do like a double landmine deadlift, one on each side)
You can also make a makeshift pulley system using sturdy cable, a loading pin, some skill and a rack or doorway pullup bar. (mine held but I never needed more than 40kg on a pulley exercise.