I have used RAWTherapee, Darktable, Gimp (all free) and have also used the free trial versions of Affinity, Photoshop and Lightroom.
In my opinion these programs can be divided into two distinct categories:
1) sorting and basic editing (including non-destructive global adjustments for RAW and jpg images, as well as some local adjustment brushes):
– Lightroom (120 USD per year, with Photoshop)
– RAWTherapee (free)
– Darktable (free)
2) Detailed adjustments and multi-layer editing, but less good for organising photos and somewhat heavier:
– Photoshop (120 USD per year, with Lightroom)
– Affinity (50 USD one time)
– Gimp (free, no RAW file support by default)
Most of your photo editing will probably be done with a Lightroom-style programme, but the more advanced editing from the Photoshop-style program and the layer editing they allow for is great when you want to do more, such as adding text or merging multiple photos. I recommend having one of each.
If you have the time to do so, (and have enough space on your computer), I would say get the free trial of Affinity and the full (free) versions of RAWTherapee, Darktable and Gimp, install them all and see what you like best. Then un-install the ones you like using the least. If you can afford the 120$ per year, Photoshop and Lightroom may be the way to go, although I personally have built my business around Darktable. I like the workflow and editing options it provides and it works better on my Mac than either RAWTherapee or Lightroom and definitely is lighter and faster than Lightroom. When I need a Photoshop equivalent I use Gimp, although Affinity would probably work better for some applications. I have tried Lightroom and Photoshop a couple of times, and each time I decide that for me, it is simply not worth paying 120$ every year for the rest of my life, even as a professional.