I have several small single output supplies now
but very quickly built a couple fixed +/- supplies
just for the convince of not having to configure and set the voltages each time.
I built a +/-12V and a +/-15V. Thinking the 15V for really old op-amps (741).
But if I were to build just one, I would build a +/-12V.
Then, you have a +12V output readily available for those battery operated projects.
I just love these little HP supplies (I have four now. Brings back the old school days.
):
Can be had for $50 on eBay.
But, I would lean toward a
Siglent SPD1305X and build a +/-12V from 7812 and 7912 regulators to get started.
Sense lines. Plus USB & LAN available for automation testing.