Hi Nikkie
I don't know if this filter info is available elsewhere on this site, but here is a brief summary.
For Landscapes etc, you only need 3 types of filters.
1. Circular Polariser (CPL). This is a round filter that screws on to the front of your
lens. It's purpose is to cut down on reflected glare from water and foliage, and can also make sky look darker blue.
They are most effective if the sun is at right angles when you are photographing, i.e not much effect shooting into the sun or directly away from the sun. You can rotate the filter to get a greater or lesser effect.
2. Neutral Density (ND) filter. These can be circular screw-on, or square like the next filter, the GND. You get them in various '
Stop' values i.e 2
stop, 3
stop etc, up to 10
stop which is almost completely black. They are a neutral grey colour, so as not to add a tint to your photos. Their purpose is to cut the
light entering the camera, to enable much slower
shutter speeds (for 'milky' looking waterfalls etc).
3. Graduated Neutral Density (GND). These should be bought in the square format, with a special holder which screws on to your
lens. You can get circular ones, but they are of limited use as the transition is always in the centre of your photo, whereas you might want it to be only 1/3 down etc. GND filters are like ND filters, tinted grey, but only half-way down, fading to clear at the one edge. They are used to darken just part of the sky, e.g for sunset or sunrise photos when the sky is much brighter than the sea or land below.
All of these filters come in different sizes to suit different
lens diameters Typical sizes are for instance 57mm, 62mm 67mm or 77mm. The filter size is sometimes printed on front of your
lens, or the specs for the
lens will give it to you.
You can buy different sizes for all your different
lenses (expensive), or a better way is to get a set of filters that fit your largest
lens diameter, and buy 'Step-up rings' which adapt larger filters to fit smaller
lenses. Don't do it the other way round, a small filter on a large
lens will vignette (dark corners). You should decide what is the largest diameter
lens you are likely to get in the next few years, and buy filters to fit that, with step-up rings for your other
lenses, otherwise you will buy a new better
lens and find your filters are then too small, and have to buy them all over again.
I am not going to recommend brands, but make sure you get a good recognised brand (eg Tiffen, Hoya etc) and get Multi Coated versions if possible. You will pay over $150 for a good CPL.
I recommend you get just one type at a time, and learn what it does before moving on to the next type.
Good luck