Depends where you live, how old you are and what job you're doing. Plus level of service within company, pay rises usually annual and indexed to inflation, you want to be sticking at jobs a fair few years unless it's ghastly. The more jobs on your CV the less likely you'll look committed.
In general 'non' London, 30 something, professional, I'd say £30k is good, £35k is really good. This would be a job that you've got experience in, possible senior, pre management. If an unskilled job like Admin/Call Centre you'd expect a manager to get £30k plus. Team Leader £25k plus. Senior Admin Asst / Senior Call Centre Op £18k plus.
Personally I would index it with age so 20 something would be looking £20k - £30k - so you're looking at good degree specific to an industry, entry level, starting above £20k & progressing onwards. You could hit £30k in a few years depending on experience and promotions, plus yearly inflation indexed pay increase.
First job between £12k & £18k depending on whether you have a specific degree for where you're working. If it's an internship more towards the top end, if a trainee more towards the bottom. Obviously YTS you're looking at minimum wage for your age group. Some do pay more and pay for qualifications including a degree, so you should take the £9k saving into account. Or if a HND/ONC however much that is.
Teenage children that don't thrive academically should look for YTS and stick at it till fully qualified. Yes the pay is crap compared to going in as say Admin/Call Centre work. But in your early 20's you'll be hitting £24k plus as a salary with all qualifications and extensive experience. If you start as an Office Junior you want direction so Accounts/Marketing/Sales, that way you have a speciality, you have training and experience, again early 20's you'll be looking st £20k plus, but in Sales you get a basic salary that is topped up with commission from sales you make. So if you are bubbly and have the personality / skills you could be an area manager in your early 20's with company car, decent basic + commission.
When I was young career education was crap, the jobs I was interested in, the advisor hadn't got a clue. If you know for definite what you want that's good. Generic degrees are only really useful for teaching, you'll need to pass a post grad course so they let you loose on children, unless you opt to study directly for Primary Schools which is a specific degree, incorporating training.