considering if u know how to shoot with MANUAL SLR then yes D90 is a good camera.. as in other camera..
it's not good when it's broken.. or not used. period.
price range is from RM3.8k to RM4k+TQ

(this answer is based on ur question)

Yesterday I go to Queensbay Mall and asking 4 D90 complete set (Body, kit lens, 2 Batt, beg, 8G memory and tripod) = RM4250.
It's OK or not?

"Manual" as in the aperture, shutter speed, ISO, white balance and etc all self set and not camera help you auto set.

Can sum1 tell me what the different with D90 and D5000?
If I'm not mistaken, Ken Rockwell more recomended D5000 compare to D90 or D300.
How bout the lens?
Can D5000 use same lens with D60 or D90?

Yes u can....but for D5000 (or other nikon bodies without motor such as D3000) u need AF-S lens to autofocus. If u use a AF-D/AF lens, u cant auto focus with it
erh..new lenses(almost) are AF-S.....my only worry using D5000 is that we cant use a lot of older prime lenses.....(of course we can, but cant auto focus lo)

I got 1 8gb, 1 16gb, 1 4gb.
Hey, I think you should stop being a spoon feed person.
Start reading before asking very very easy question.

There is pros and cons of SSS.

Here's 2 magazine you can buy and learn tricks about photography,

-Digital SLR Photography
-Digital Camera Magazine (aka DCM)

But like zellleonhart said, you still need a camera in the end for pratical practise. Count your budget and let us know so we can tell you what you can make out most with the money you have.