Not an entry, but I never balk at giving advice
1) Don't be shy when buying used knives. Ask about walk and talk, gaps, blade play, cracks, weak springs, other flaws and defects. If the person selling the knife isn't familiar with nomenclature, you may have to patiently explain these terms so that they can check it out for you. Far too often I will pull the trigger on a great-looking knife only to find that it is just a broken-down wreck that was mis-represented on an auction site and that I was too excited to investigate further.
2) GEC, Queen, Case, CSC are doing great work today but do yourself a favor and find some pre-war antiques. You'll appreciate the modern knives more once you see the traditions of craftsmanship and innovation from which their current production lines are derived. And, if you're finding pre-loved patterns and specimens, you can just clean/sharpen them and drop it in your pocket.
3) It's good to identify your goals early and often. Are you a collector, accumulator, user? Do you not feel like defining your hobby and just want to go for it? But, that said, don't be afraid to branch out. I find that one of the most satisifying yet accessible branches of this hobby is the collection and use of traditional working patterns from all over the world. And because of their humble origins, those kinds of patterns rarely break the bank. Opinel, higonokami, Okapi, Douk Douk, Mercator, Moras, SAKs, German sodbusters...the list goes on.