Skateboarding
it all depends on distance to subject/skateboarder as the closer you are the faster the movement appears (if this makes sense)
try around 1/500+ shutter speed
aperture shoot wide open, enough to keep your subject in focus, again depends of distance/focal length, you want to blur the BG, this looks particularly nice in skate parks with graffiti as you can get nice creamy colours
best to do is use shutter priority, try 1/500, play a bit till u like what u get


Landscapes
aperture f/11 - f/16
about 18-35mm normally works well


Portraits
this varies considerably depending on what you going for
also greatly depends on distance to subject, indoors/studio or outdoors etc
f/4 - f/7.1 for outdoors etc
studio (fasion style shoots) you generally shoot with a high f# as you have control over you BG and want more detail on your subject


ISO
its always said keep it as low as possible, which is right, but with sensors now days don't be afraid to push your iso up if needed, 1600 is certainly no problem for dslr's now

these are just general guideline
post some pics for c&c and we can guide you better
or post some other photo's you have seen/like and we can "guess" the setting for you to try produce similar

Next question.



I shoot Continuous frame shots, and I want the best way to upload them to the internet.

These gifs are looking like garbage quality.
Is there another way in Photoshop to make them play through in high quality. Or should I just make every image in it smaller and make a collage out of it?

cant help you there

Use a flashgun for indoors and learn about white balancing.

I don't care if you shoot continuous photography, you should never save high quality photos as GIFs. that defeats the purpose of owning an expensive camera.

the best thing that I could think of is for you to learn Javascript or Flash if you want to animate or create slides for your photos