If you do a search of the forum you will find a lot of lens discussion and many "affordable" options.
As you have the EF mount you won't be able to adapt the FD lenses as the flange focal distance is greater so the adaptor would need a lens element to correct the FFD so the lens can achieve infinity focus. This would affect the image quality and so would probably not be a good investment.
With the EF mount you have a limited selections of lenses you can adapt. You could look at old Nikon or Leica R lenses.
Nikon AI and AI-S lenses all work well but there are not many wide angle options. 24mm are easy to find. 18 and 20mm less so. Not many options wider than that that are "affordable".
If you are looking for wide angle lenses for the EF mount your best option is probably the Tokina 11-16mm.