My kit is built up of many sources over the years. Nobody regrets buying quality. I managed 'reasonable quality' most of the time.
Spanners:
Aigo R&OE metric set, very traditional design (read heavy and well-ribbed) and made in Japan, had them 25 years and they're still going strong, augmented by Powerbuilt and Craftsman for those funky euro sizes like 16 and 18mm. Recently added King Tony offset ring spanner set, bought in preference over Teng as it was 25 bucks cheaper and had a more useful couple of sizes. It's not beautifully finished, but is very serviceable. I have Craftsman flare nut spanners that have had light duty over 20 years and look new.
Sockets:
I have plenty of Craftsman (unconditionally guarenteed forever), some Halfords (time served in UK), Powerbuilt, and odds n ends from Proto, Sidchrome, Koken, King Tony, repco. Recently acquired Jonnesway (impressive finish and reasonable pricing from BNT) sockets. latest acquisition: Powerbuilt flex socket set 3/8" on rail, beautiful. Ratchets - mostly craftsman. You can't go past a good ratchet.
Screwdrivers:
Belzer (unobtanium these days), Witte, Snap On (indestructible and likely to outlast me), and the Powerbuilt seem pretty strong-tipped these days.
Sets? Here's my 2c worth:
Get a couple of good quality ammo boxes military surplus. 5.56 box for 1/4", 50 cal for 3/8". They're strong, easy to carry, and have a O-ring seal. Buy cheap socket rails in 1/4, and 3/8. lay out your sockest on the rails in order, make a list of the gaps - go buy them (on sale). Now you know/can see if anything's missing. No need to throw out your baby (your current tools) with the bathwater. Always have a rag in your toolboxes to clean your kit before putting it away - then its ready to go next time.
Sizes? All of them.
As somebody else said, you're going to need the lot working on Euros. 1/4 and 1/2, though I've been finding the really tight stuff 1/2" is just too big - 3/8 is called for also. Torx, Deep, standard and even flex sockets. Wobble extensions and Universal Joints.
Brands?
Of the brands I've isted above, they're all very seviceable. Never broken a socket. Plating has chipped on a couple of sockets through abuse on rattle gun or very long bar. Buying in NZ, Powerbuilt, Teng, King Tony, Jonnesway, even Repco seem pretty reaasonable.
Facom and Stahlwille look beaut, but not justified on my budget. I like Koken but am too tight to buy a set.
Rather than select a fave brand, I'd find a good tool supplier and stick wth him. When I started acquisitions I had a tool rep who had me on his monthly calling list - I was in an office environment rather than a workshop, but he knew what I wanted and my money was good enough for him, and I got good kit at good prices.
Hope you enjoyed my brain-dump.