I'm deeply, deeply biased in favour of bell tents (no! I hear you say), but they are not reasonably priced (my 5m souplad hybrid was £400+) unless you can be arsed to drive nearly to Germany and pick one up from Obelink and unless you buy an inner tent (sold separately) they are sleeping/living/everything all in one. They are bloody heavy to lug about.
However.... compared to tunnel tents and bendy pole shenanigans, they are an absolute DREAM to put up/take down, they are very stable in the wind, they look FABULOUS and will last a lifetime if looked after properly. They are also cooler inside in the hot weather and have a wonderful, wonderful zen calmness about them. And you can stand up in them (big plus imho).
They do lend themselves more towards glamping, but then you need the means of transportation. Our estate car usually ends up stacked to the ceiling and the 2 seats next to DD in the back piled high too. And that's without all the silly pretty stuff I'd love to take along.
So, having put you off bell tents , I only started camping properly last year, and some stuff I bought I've found invaluable, others not so much. Basically my useful and necessary stuff includes:
Sleeping
Good quality sleeping bags
Some kind of mat to put between yourself, your mattress and the ground (Tesco do silver-backed foam mats quite cheaply)
I bought airbeds but having heard all the good things about SIMs on here I quite fancy getting them and dumping the airbeds. Airbeds tend to be colder, and to avoid this I put a fleecy undersheet on them and then a normal fitted sheet, then a throw on top of the sleeping bag. Which looks lovely and glampy when they're made up as beds/lounging areas during the day, but adds considerably to the packing burden...
Airbeds need a pump
Cooking
Coolbox of some kind and ice packs - there are loads of threads on what sort is the best to get for your needs.
Stove of some description - I initially bought a Trangia and it scares the shit out of me, however all the pots & kettle fit so neatly together and it's so light I tend to take it along as my set of pans and not use the burner. Otherwise I've got a double burner camping stove that uses butane bottles. People here swear by Cobbs/Cadacs and they look fab, but are £££
Something to put the cooker on - you can stick it on the ground but you'll get backache, plus a windshield attachment thingy is useful.
Lightweight pots/pans if not using a Trangia
Something to eat off - some people use those cheapo plastic picnicking sets, others 'proper' melamine, some just take paper plates and chuck them on the way home!
Other
Chairs/Something to sit on - again there are tons of threads here and on UK Campsite about which is best/comfiest/packs down smallest. We started off with those folding chairs they seem to sell in every service station in the land, and have just upgraded to Moon chairs. (Nothing wrong with the folding chairs, they were fine and comfortable, but I wanted a wee bit more comfort, being a wuss)
There is loads of other stuff you can get, I'm sure I've forgotten loads, but that's the basics... and while I've typed this essay out I'm sure loads of others will have replied more usefully!