How should I start my own home lab?

I suggest that you pick a project, and get it done. Use the most common hardware you can.

Buy a labeling machine and label everything that is not known good. If you have SD cards, label cases explaining what is on them.

Get a large HDD in your desktop PC (or some kind of mass storage) and back up pics, notes, code, etc. Keep it forever. Keep at least 2 copies of it.

Buy plenty of plastic drawers. https://www.google.com/search?q=plastic+drawers Label them with the labeling machine (1" black text on white labels work the best. If the labels do not stick, stick duct tape to the drawer and stick the label to the duct tape.) Organize every part in plastic drawers.

Then pick another project and get it done.

Don't give in to the temptation to rack-mount everything or to build hardware for possible future use. Just do one project at a time.

I would suggest you to skip all these "cheap" solutions and get a used Dell T20 with a Xeon v3 and 16GB ECC Ram... it is about 100 bucks and way more powerful than any small solution, and 33watts idle power consumption with 2 10TB HDDs.

If you wanna scale up, you could re-use the Dell T20 as NAS only device and buy a more powerful server hardware.

You could also get one of these lenovo mini devices as a server, but I invested some more money and got myself a still cheap but very power efficent Fujitsu D3417-B2 Board about 9W idle.

See e.g. https://www.youtube.com/watch?v=MucGkPUMjNo

As Software / OS you could start with TrueNAS Scale or Proxmox.

NASA has a document on how you can build a Raspi supercomputer cluster. You may then want to crunch the data they have opened access to for visualizing space phenomena filtered according to your taste. The Raspi company has a magazine containing projects to try.

I started really small with my homelab:

  - Got a couple of Raspberry Pi's and connected them to wifi.
  - Installed https://k3s.io/ on them. One master node and one agent/worker.
  - Started adding workloads
  - Now I have PiHole, Tailscale, Promtheus, Grafana, Mimir, Homebridge, a custom Go app that I use to create a bunch of metrics, eg. from my solar power system, etc. 
  - Also added another agent/worker over time.

So start small and easy then go as fancy as you want depending on what you learn/play with.

Use old laptops. Great option as long as you don't need a lot of computing power.

  - cheap
  - come with an integrated UPS
  - come with an integrated console for debugging (keyboard/screen)
  - usually more efficient hardware than a desktop, and certainly a server
  - quiet

RPi's are still wildly overpriced & hard to find, and the Pi-alikes often (usually) have support issues (out of tree patches required, lots of opaque blobs, etc). I like my home-lab to be about learning new stuph, not being a beta site fighting underlying platform issues (aside: I confess that I do have one RPi-ish cluster (3 boards), but more and more it's being used for "I need some GPIO for this" and way less for 'compute'). As many folks have mentioned, pick up a couple of x86 mini PCs/SFF (new or refurbished depending on budget). FWIW...I've had luck with small, low power devices from Protectli, Seeed and Minis Forum. Problem solved; heartburn avoided.

Someone mentioned "r/homelab", which is pretty interesting/active if you can stomach Reddit.

VMware has a 'free' ESXi license for homelabs (no cost, many restrictions apply). It'll run on many/most of the small PCs out of the box; 7.0 ran perfectly on my Seeed Odessey. Yeah, I need to spend more time with the various newfangled OSS hypervisors, but I'm used to ESXi. Get off my lawn.

I personally think having a managed ethernet switch, particularly one you can do VLANs and netflow and/or port mirroring is helpful in a homelab. VLANs help you build more complex scenarios, and sometimes you really want more visibility about what's going on on the wire. Refurb Cisco or Dell switches work well (and tend to be very cheap), but also tend to be noisy and power inefficient. I don't have a ton of experience with the newer generation of probably more efficient 'desktop' smart switches like Zyxel, TP-Link and Ubiquity.

The subreddit r/homelab is full with tips for you own homelab. They also have a start readme: https://www.reddit.com/r/homelab/comments/5gz4yp/stumbled_in...

I thought about getting an RPi again recently - but they've gotten hideously expensive (if you can even find them in stock anywhere)

They still look kinda neat, but if you really want to run your "home lab" at "home", I think you're better off getting an SFD or similar and running VirtualBox

Personally ... I don't want more stuff running in my house, and prefer to pay someone else a couple bucks for the server to run in their datacenter :)

(Of course ... that's probably not gonna work if you're wanting to "do something cool" with other data/systems you have at home)

This will not be popular but you don’t need ECC or Xeons.

You can find great deals on powerful PCs from eBay sellers who are IT recyclers.

I’ve found the SFF/Mini PC’s to be great.

You also have to decide what you want to do. And if you want the headache.

For example it’s easy to start doing home automation, dns server, NAS. When things break or updates break things and nothing is working and you have to pull it all apart again was to much for me.

I bought a few 8th gen intel NUC mainboards off of ebay. I loaded them up with an SSD and RAM they work very well. Depending on how you want to manage your containers/VMs, a hypervisor is something to look into. I've been trying Proxmox on all my NUCs and they perform great, but there are other hypervisors out there.