These CPUs make for an exceptional performer. While power consumption is much to be desired. They tend to be quite powerful and found quite cheap.i think these are still decent budget offerings
MB
The mucai h61 is a pretty decent MB. Extremely cheap can be picked up for as little as £13 on alliexpress I can speak from experience having used my h61 for 7 months now
Intels own brand of MB can tend to be quite cheap and can be picked for as little as £15. Do research into the model of intel MB you'll be getting as these tend to be quite finicky from what I hear.
If you've got a bit more to spend. I advice you go for the AMD Rx 480/570 or perhaps do what I did and save. I managed to get a gtx 980ti for a whopping £20.
PSUS
You should never cheap out on your PSU. Get a cheap name brand if possible. I recommend checking for old stock. And display items it's how I landed a Corsair CX550.for a whopping £27.58.
For a low end, small, low consumption Intel box for HTPC/Kodi, Home assistant, Frigate, small Home Server or all of the above, I can recommend any N100-based box or mini itx mobo. It's very fast compared to prior Intel low consumption CPUs (apollo lake etc), does 4K, HDR, AV1.