The mainboard alone doesn't need very much power. What about the CPU and graphics card?
This one is of high quality and has enough power for most components you can install:
be quiet! STRAIGHT POWER 11 (650W)
How many watts you need can only be said with all components together.
You can also calculate it here: https://outervision.com/power-supp...
(I recommend rounding up a little (50-100W) to be prepared for later upgrades).