Hi
@MSX welcome to GTPlanet! Please ignore any minor spats on this thread - this is a big site with many very passionate people and they all have different views.
If you are buying the wheel new it does make sense to pick one that is PS4 compatible so look carefully at the T150, T300 and G29 - any new wheel that isn't PS4 compatible will collapse in value as the market will be flooded with them when their owners upgrade to PS4 wheels for GT7 (from experience I have seen the price of wheels double in the UK when GT5 and GT6 came out as demand rose so I know the market is very volatile) . Don't rush your decisions because that makes you more likely to make a bad one and you may be stuck with a worthless wheel.
A bit more about the DFGT in case you do decide to go the secondhand route - the wheel is very good, but it does not have flappy paddles - there are buttons on the back of the wheel which line up with your fingers. Some people fit aftermarket flappy paddles made by Gran Turgismo (there are details in the sim hardware section of this site). I did not have a problem with changing gear using those buttons and neither have the many people I know who use that wheel (it is the most commonly used wheel - which makes it madness that it will not be PS4 compatible). It is accepted as being the minimum standard for a wheel (cheaper wheels than this generally do not have force feedback and will therefore lap slower than a hand controller and must be avoided). The foot pedals work fine, but they have almost no resistance - all the money obviously went into the wheel. Some people increase the resistance of the brake pedal with bungee cords, squash balls, bits of tennis ball etc etc and there are threads which cover how to do that on this site and tutorials on youtube. I felt no need to increase the resistance during the time I had a DFGT and used it as standard.
In my view you are coming at this as an enthusiastic novice - rather like I was except I had more road and track experience - for that reason I suggest that you pick up a copy of GT5 as well as GT6. You can only play GT5 offline (i.e. you can't race against other people), but I think it will give you 3 months, or so, of enjoyment. The reason for suggesting this is because it has many license tests, all of which will improve your speed. It includes an excellent feature where you do the Nordschleife (Green Hell) track in sections in gradually faster Mercedes cars. There is also a rally tutorial and a Nascar one. For learning about driving lines via doing license tests it is better than GT6 and as a novice I think you will find it very enjoyable. I'm guessing that you could probably get a copy for about 10$ and it would be a great way to start. there are many tests to complete - it is easy to get bronze, hard as a novice to get silver and some gold levels are very difficult and take a lot of practice.
When you start - don't do so with the intention of racing through and getting gold on everything as quick as possible. If you have a wheel, in my view you should start the game with all driving aids off (with the exception of ABS on 1 and the possible exception of the driving line until you have learnt a good line). The reason is that you will learn how to modulate your throttle position and make your steering inputs smooth and also you will get more feedback from your wheel and a feeling of control - sometimes right on the ragged edge - the driving aids take this away and turn you into a passenger). When you start you can also try doing all the license tests using the interior view, which is generally slower and harder, but more immersive and leaves you with the option to switch off the HUD. When you later start racing with other people you may find you need the bonnet view to get better visibility.
Many of the people who read this site and some who have commented on this thread are unbelievably fast drivers - they are probably too modest to tell you that. I consider myself just an average driver - I have high enthusiasm, but I am not a fast driver - I found some of the driving challenges difficult to achieve gold on (especially in GT5). I found GT6 easier and a less satisfying offline experience than GT5 and it taught a lot less about driving.
So in summary my advice is get both GT5 and GT6. Don't rush either game - savour the experience and spend 3 or 4 months on GT5 then progress on to GT6. When you are getting easy golds in the seasonal time trials start thinking about racing online in one of the many leagues or championships run by GTPlanet members. Mine specialises in classic cars, replicating historic race meetings or series. There are series or one off races to suit every taste in motorsport. I tried online racing on GT5, but found I wasn't fast enough so put in a year of practise then tried again and decided to run my own series.
If you use the public online service in GT6 you are likely to have a bad experience - quick match is best avoided as the other drivers are not interested in clean racing and you just get rammed off the track all the time. The same happens in open lobby which can be full of kids driving the wrong way etc. better to practise alone first then look at the online racing section of GTPlanet and try out different leagues or championships etc till you find one you like. Some of the larger ones have multiple levels - you start in a lower division and progress through as you get faster - this gives you good close racing. Some Hosts run mixed ability rooms, but award license grades - typically the fast drivers will be called Pro and the slower guys Am - the host can even the field with different tyre choices or multi-class etc.
If you enjoy your wheel and GT5 and GT6 you will definitely love online racing on GT6 against good, clean drivers - but that is probably about 6 to 9 months away for you now if you follow my advice.
You can use a shifter with GT5 and GT6 - I don't normally miss shifts, but you won't race with a shifter. I save the shifter for if I want to race in arcade mode in a Shelby Cobra or perhaps do the night race again at Mount Panorama in a Lancia Stratos using interior view and HUD off for maximum realism. I use a Wheelstand Pro with a comfy leather sofa, but I couldn't achieve the perfect shifter placement to match my daily driver so I built an 8 inch wide sofa module to match and fit the shifter (Thrustmaster TH8RS - now superseded by a TH8A).
Regarding stands - I have two friends who bought the Omega - one couldn't adjust its position enough to suit his chair so he had to get another chair, but they are both happy with the stand. I know at least a dozen people with the Wheelstand Pro and I've had two personally and been very happy with it. Some people criticize the design for having a central pole and assume that it will impede use of the heel toe racing technique on three pedals - I don't think they have actually tried it - it doesn't impede me - it's only lack of talent that impedes my heel toe technique, my neighbour who is a proper amateur racer has no difficulty. Some friends use a Wheelstand Pro with an old car seat mounted on a piece of wood and one friend started with that setup then transferred to a full rig.
Finally don't rush anything including your buying decisions - there is plenty of time and it will take a long time and a lot of practise to get good. GT7 will probably not be available until Christmas 2016 at the earliest so you can take your time progressing through the games (Note I have no special knowledge on the release date), but I think you can get a lot of enjoyment from a PS3 until then. Some of the very fast, expert drivers have moved on to PC's or other games on the PS4, but as a novice used to GT on the PS2 I think you will find GT5 and GT6 on the PS3 very enjoyable.
Below my shifter:
View attachment 455363