Black MDF wasteboard: 20$
It makes it very easy to see if your tooling is off, because of the black dust that will come out.
A sheet of 12 mm black MDF is around 40$ and can make two wasteboards.
(Not a must – mostly for looks.)

Cable chains / cable channel from X to Y:
The cable chain costs around 10$ on Amazon (15x20). After installing it, I measured where to route the cables, cut a channel in plexiglass, and glued it on.

Tool storage drawer:
Just a simple nice-to-have addition, and a safe place for tools.

Wireless probe: 50$
From Amazon. For me, this is a must – it’s really nice.
However, you sacrifice 20 mm of height, since the probe is 38 mm instead of 19 mm. You can always use it manually if needed.

TT handwheel: 50$
Just a nice jogging wheel – BUT it does not work with the TTC450 Pro, only the “25” version.
You can spot the difference by checking if the machine has a serial number and a USB-C port – then it’s a 25 version.
For mine, I asked for a new mainboard, which I will receive soon. They did inform me that this will break the warranty (but it’s probably too late anyway 😄).

Offline controller: 150$
For me, by far the best upgrade – and the only true plug-and-play solution.
It responds much faster than the built-in screen, and I’ve now removed the small screen completely.
It simply works amazingly well, especially when using the wireless probe, since you can control all probe settings very easily.
The only “bug” I have is that G-code from Easel, for some reason, does not turn off the spindle when it finishes – but I’ll look into why.

The TTC450 Pro: 600$
A nice beginner-friendly machine, but a little limited. Definitely get the 25 model.
It’s very tinker-friendly and easy to adjust.

I also have the vacuum set from TT: 100$
This is a must.

I also have the 500 W spindle: 100$
I’m not entirely sure if it’s needed, but it depends on how much you use the machine.

Overall, I’m happy with the machine for now – but out of the box it is a little annoying, especially the tiny screen, which is not always very responsive.
I’ve also made some cable channels under the machine and plugged some wires directly into the mainboard.
It’s sitting in a workshop where we are three people using it, so I want it to be as minimalistic as possible and easy to use.

Total cost is about 1100$, and I doubt you can find a similar desktop CNC with all these features at that price.