The only lens I initially had for my A7 was the Sony FE 28-70. I soon got interested in a Sony Zeiss FE 24-70. Now I never use the 28-70 and intend to sell it. The difference between 24 and 28mm is small but worth it, IMO. The 24mm is wide, but not wide enough to introduce the extreme distortion that you often see on wider lenses.
My best prime lenses are the Minolta 200mm f2.8 G (white) and the Minolta 300mm f4 G (white). Both very sharp lenses and the 200mm is light enough to actually carry around, not so the 300mm. The worst lens I have, be it prime or zoom, is the Minolta 28mm f2.8. The biggest difference I can see between Minolta and the latest Sony lenses is attributable to the newer coatings, not so much the glass although that probably does also, I just cannot see it unless you go to the G master lenses. Make sure to get a good condition lens. I also have the Minolta 100mm f2.8 macro (D) which is a superb portrait lens. Many Minolta lenses are still comparable with newer lenses and are a fraction of the cost and you can improve them slightly by not using a UV filter and being a bit more careful.
Full frame is certainly the way to go although it is more expensive. However it is the lenses that really break the bank, not the bodies and you have a few FF lenses I believe, so your 75% there.