if follow the aspect ratio should be "normal"
or because you feel something has been cut, so you feel abnormal.

I suppose as long as the ratio of the photo remains the same, it won't feel that awkward?
I used to crop without fixing the aspect ratio and in the end the photos turn out too squarish haha, very obviously cropped and looked very weird 
Nice camera that one
Wise choice 

I think its very hard to get attractive shots without retouching nowadays The closest you can get is through strobes I think 

D90 is pretty okay ma, not really worth upgrading to D7000 or D7100.. better wait for more advanced DX cameras only jump?
In the meantime, improve skills or glass 1st 

   
Bro, I had such dilemma like you last time. Like what sifu TJ said, save the $$ for your glass or direct upgrade to FX. You can retouch on the photos you took from your D90 to look better. Anyway, skills are very important too. 

Practice makes perfect~
Watching videos help too! You'd be amazed how much a simple adjustment will affect the final effect of the photo yo 

looking at sites full of professional works will help you to get the "creative vision" imo.

a good example is 500px, always feel inspired looking at all the good photos.

shoot more la, try out different kind of photography like portrait, cars, sports macro, landscape and so on. When you found the type of photography that suits you the best then you try to be good at it after that you move on to learn other type of photography

just dont think that you are already good at it so you stop learning, continuous learning is the key to success

Oh no, I wasn't referring to the videos on photo editing haha, even I don't really fancy those..
I've seen some that teach you how to deal and make good use of natural light (from B&H I think). Its amazing how much improvement you can achieve by simply changing a few things (like taking shots under shades, avoid having the model directly under harsh indoor lights etc.)- many of which we often overlook while taking photos   

Yes yes, go set up account so that we can stalk you haha

yeap that's me i submitted a lot of photos to sifu kentang's site. too bad the site is kinda abandoned now

True.. haha but skills come in practice so.. yeah, need shot more.. I also lazy, so now trying to create a theme shoot with objects and lightning at home.. no need go out  I was super interested in streetshot, but no time go out so opt another route.. haha but still love street photo thou..
As for in door, GYM has very dim light, so the kit lens very hard to take good photo.. Try get a prime, like 50mm f1.8, or 35mm f1.8.. these shld do a better job indoor.. or use a tripod to compensate the long shutter.

I've tried the Tokina 11-16mm f/2.8, and doesn't seem distorted in my eyes thou.. LOL may be I too noob to distinguish what is distortions thou.. all pics looks awesome to my eye.. 
home experiments is good for lazy people.. haha

in the past when i use that lens..also didnt saw any distortion..
i think need a lot of straight line then only able to tell it guah...