Have you made sure that its not the mirror that's dirty?
Might be a bit risky to clean it yourself since you will risk damaging the sensor
maybe can ask around shops around your area? Its better to let the pros do it for you, usually they charge around RM50-100 for the cleaning over here 

So humble haha
I don't know how to take landscape shots one haha, please teach me next time 
Dry and soft cotton buds will do, but please be extra careful and make sure there are no dirt/sand particles on the soft cotton buds. Its rather unlikely that the sensor is dirty for a new unit? Unless if you switch lenses alot

For your current or recent photos, you can always spot heal those dust particles 

The kit lens is pretty much a multipurpose lens designed for beginners, you'll need to get dedicated lens to go further.
Landscape => go with wide angle lens, on a DX like D7000 its like below 20mm focal length.
Portrait => 50mm 1.8D. 35mm or lower for full body shot.
Kit lens can do the job for these photography, except bokeh effect on portrait.
So if you truly want good portrait, get either 50mm 1.8D or better 35mm 1.8 DX
Now waiting opinion from real sifus 

the only advise i can say is turn your kit lens to 35 and 50mm and look around see it fit or not so you can nail down which focal length you want.

as for aperture it can't be done, but you can go times square nikon center and ask the people there to play with the lens. FOC 

for portrait people prefer use 50mm on DX becaues it is around 75mm (or 85mm prime) which many sifu using for that.

or ask your friend bring 50mm (if can 35mm too) borrow you walk around and try use it so you can decide want to use or not.

You can play with aperture actually, just that AF-S lenses don't have aperture ring and the kit lens' aperture are too high to easily do bokeh.
50mm are more affordable, but I'd say 35mm is more functional, moreover on DX for full body shot.
So if you can afford it, go with 35mm. Probably around RM600 for 35mm f/1.8 DX.
Dunno about AF-S, but 50mm f/1.8D are usually below RM300.

hmm back to root question, what makes you to think to get 35/50mm prime lens? 

aside aperture of course prime lens can get as low as f/1.8...

just because you hear your friend own that lens? 

get either 35 or 50
then u can learn to frame a pic, composition at a fixed focal length
bokeh wise, doesnt matter la, as long as u got ur subject in good composition in your frame
anyway, go try out the lens first then shoot more and more and more.
keep shooting and happy shooting   

if i were you i wont bother about 50mm 1.8, i would go for 35mm, i've tried both and 35mm is better for tight spaces and slightly better image quality

Hoho, good to know that you are a Nikon user 
Great camera there mate~
How long have you been using (not just owning) the kitlens? If you are still new to using the 18-105mm, then just stick to it a bit longer. I really love that lens haha, most people don't really know how to appreciate the lens (including me) until later on when their photography and editing skills become better (i.e. when it sort of becomes irrelevant what lens you use to take certain photos). Hell it can even be used for macro! @@

The 18-105mm is suitable for almost all genres of photography in general apart from landscapes. So it all depends on you, if you are really interested in landscape, then a wide angle lens is the one to use. But I still think you can just stick to the 18-105mm for the time being, its not like its not capable of taking landscape shots at all la haha 

When to buy new lens you ask? When there comes a time you think that the 18-105mm can no longer satisfy your needs because of hardware limitations (not photographer's limitation ), then its time to change. By that time you no longer need us to tell you which lens to go for already 

shoot on weekends or holidays

i duno, i prefer say you better stick it first then decide later, at least go borrow your friend's one play it first then see need to waste your moneh or not haha

Hey there bro. 

You need to start thinking what kind of watermark you want - one with words only, with a logo, or with both. Then work towards that.

An Orb Weaver Spider, before and after laying its eggs!
Note the huge decrease in abdomen size (becoming deformed altogether). The process is probably so stressful and straining that the mother will die within a few days- a huge sacrifice for the sake of continuity of the species!

A fecund Orb Weaver Spider- Parawixia sp. ♀ by PF T.J., on Flickr

Orb Weaver Spider- Parawixia sp. ♀ by PF T.J., on Flickr

For more photos and guides on Macro Photography, please check out my blog: http://pixelsdimension.com/