The Gillet Vertigo can win the Gran Turismo World Championship with great difficulty but not impossible to win. A race report with 6 races in the GWTC can be found here...
Gillet Vertigo in the Gran Turismo World Championship.
It is hard to get a good setup from the car due to the lack of downforce...but Team666 has a good setup which can be found
HERE
Also get rid of the Turbo, due to the lack of downforce it cannot handle at high bhp values...and you need to practice with the car.
To help you out on what lineups and cars you will face...I have recently done the PAL Version of the 52 lineups of the Grand Turismo World Championship. Do not worry if you got NTSC or the Japan version....it will give you an idea It can be found by clicking the link below:
52 PAL LINEUPS OF THE GRAN TURISMO WORLD CHAMPIONSHIP
Ok if you do not want to handle with a Gillet Vertigo, then here are my views on other rides for the GTWC
By the way using the Polyphony Digital Gran Turismo in the GTWC is an overkill and is not skill.
If you want a very easy ride in the Grand Turismo World Championship with another car then get the Minolta Toyota 88C-V (From the El Capitan 200KM Endurance Race), Nissan R92CP (From the Fuji 1000KM Endurance Race) or the Nissan R89C (From winning Driving Missions 30-34) and a new Mazda 787B (From Mazda showroom bought for 3.5 million) But they are all too easy!!! Also buying the Playstation Pescarolo Judd Race Car for 4.5 Million and having a good setup is easy to win as equipped with either R2/R1 combo tyres, you will not need to pit for most of the races except Hong Kong and Opera Paris. Found out the first time I did it with this car, these rides I have done the series are well too easy to win the Grand Turismo World Championship with practice.
A bit of a challenge but will get the job done are a used Black Mazda 787B will handle as well as a new one (bought on Days 694-700), new Toyota GT-ONE (Bought for 3.5 million at the Toyota showroom) The Audi R8 (Won from Sarthe 1 endurance or bought for 4.5 million in Audi Showroom), BMW V12 LMR (Bought for 4.5 million in BMW Showroom), the Bentley Speed 8 (Won from Sarthe 2 endurance) the Pescarolo Peugeot Judd Race Car (Bought for 3.5 million in the Pescarolo Showroom)
If you want a challenge (which I like and prefer) then buy either a used Toyota GT-ONE (Bought on days 694-700), a new Nissan R390 GT1 Race Car (Bought from Nissan Showroom for 4.5 million) or even a used Nissan R390 GT1 Race Car (Black edition bought on Days 694-700), AMG Mercedes CLK-GTR Race car ’98 (Won from the DTCM Championship) and a Chapparal 2D Race Car (Bought From Chapparal Showroom for 1.1 million) All of these cars in the list have proven to win the Grand Turismo World Championship.
I personally prefer not to add a turbo onto a car or even go with a car that is overkill. As well I do not qualify in the GTWC except in the Hong Kong and Opera Paris as they are both difficult races to win without qualifying first. Anyway qualifying first does help if you have trouble though.
So pretty much you need to practice with the car...have some good settings with the car and good luck. Look at GT's race reports for an idea on how to beat the GTWC which can be found
HERE.
Thats my 2 cents worth, good luck.