What Do I Have To Do To Run FSX Smoothly? Graphic Card?

From my perspective you have a good CPU, just about enough ram (8 would be nice) but your video card isn't up to par.
You need a good (minimum) 2gig card to have better fps especially if you are going to buy such a graphic intensive aircraft.
AI eats up a video card and CPU...as does extra scenery,
I hope you have at least a 750w minimum power supply to run everything.
Older computers can be pushed just so far.

Thanks!!

Hi again... i just wondered.. you told me to get a graphic card with 2gb at least... but the card that i have does already have 3.8gb.. so if i buy a card with 2 gb, wouldn't FSX lag even more?? or is it quality it depends on?? like, for example: is it possible to have a bad 4gb card, and buy a 2 gb good card, and then run FSX better than the 4gb would have done??

As you see in the specs tab you only have 512mb to 1 gig on your present card, not 3gigs.

http://www.amd.com/en-us/products/graphics/desktop/6000/6450#

That other card that you saw on eBay, I gave you links to it showing that it wasn't a "gaming" card.
Those are the things you have to look for.
I posted a new review link in the Hardware Forum of prices and strengths of many of the latest cards, check that out.
Anyone selling a card will build up the description, these reviews are just that...reviews.
They have nothing to gain by building up the reputation of the cards.

best cpu for FSX is the i5 6600k, you don't need an i7, if you go to userbenchmarks and compare the i5 to an i7 in gameing, there almost the same %, the i7 is for content creaters, I have everything set on high with orbx scenery and still get 45 to 50 FPS, over 100 FPS without scenery