I'd say bare minimum cheapest setup for $100 is:
- [T-16000M flight stick](https://eshop.thrustmaster.com/en_us/t-16000m-fcs.html)
- [DIY IR head tracking](https://www.youtube.com/watch?v=M_VN4mMA6Cw)

If you don't want to DIY the track IR I'd recommend getting a premade Track IR from [grassmonkeysimulations](https://grassmonkeysimulations.com)
(But it gets pretty expensive there). You might be able to find cheaper solutions elsewhere to avoid DIY.

I wouldn't go for the TrackIR5 by NatruaPoint because it's ($50) more expensive and doesn't have a wireless solution for the headset. As far as differences between an opentrack and trackir5 solution, I have no idea and I haven't ever found someone comparing the two. Heresay is that the TrackIR5 has better software that is easier to use than opentrack but it's got the same quality after you have your curves setup.

For my current setup I have the:
- Track IR: monkey king sensor Camera from Grassmonkeysimulations
- Flight Stick: T-16000M
- Rudder Pedals: VKB T-Rudder Mk IV

Rudder pedals aren't needed but I'd say they are the next place to upgrade if you don't have them on your initial setup (Followed by throttle after that).

I settled on the T-Rudder Mk IVs after watching a ton of reviews on different products before being convinced after watching [this one](https://www.youtube.com/watch?v=Pk1huZqKufA)

As far has HOTAS / HOSAS / HOS options I think [this video](https://www.youtube.com/watch?v=-scnzIQdCec) does a great job giving an overview on all the options out there.

Personally if I were to start over I'd swap out my T-16000M with a [Gladiator NXT EVO ‘Space Combat Edition’ (standard, not premium)](https://www.vkbcontrollers.com/products/gladiator-nxt-evo-space-combat-edition-right-hand?variant=39887803580534)

I am missing a dedicated throttle which has its pros and cons, for one I have much more desk space free, and it's really easy for me to just put my flight stick away when I'm done flying. But as a con I don't have the most precision when it comes to flying in formation or tanking etc. When I am flying in parade I end up having to rapidly flick my throttle back and forward to compensate for the lack of precision. So my next upgrade when I get the chance is to get a dedicated throttle and find some elegant solution for storing my HOTAS when I'm done.