So I'm looking into getting some GND and ND filters. I'm not so much concerned w/ brands as I am with what ones to get (2 stop GND vs 1 stop etc).

I know ND filters come in sets, but I don't know how they're packaged (1 stop 3 stop 5 stop?etc).

You'll need the adapter ring, the holder, and then the filter themselves.

Sets vary and you can usually customize em. This place has good prices: http://www.2filter.com/

Look at Lee, Hi-Tech, Singh-Ray. Good luck--gets expensive.

I was just gunna go with screw in filters. Are they not good enough?

No, you have no control over the graduation with screw on filters. The only use a screw in filter would have is if it is just a regular ND filter and not a GND. Slide filters are the way to go with GND. Don't buy the Cokin ones. They suck. Lee or Hi-tech are good brands and still affordable.

Might not hurt to get a 2 stop soft edge GND and a 1 stop hard edge GND to start off with.

I for one second Lee slide filters, do not go with coken...they absolutely suck, you'd probably be better off taking a piece of glass and holding a match under it to blacken half of it than with buying coken crap.

I have to disagree with saying cokin filters are crap. a LOT of their filters are crap, but they have some really good ones as well. The sunset filter for instance will make a faily normal sunset simply amazing. Unfortunately more people use this filter in normal daylight to try to make it look like there's a sunset, which just doesn't work

Cokin ND/GNDs have been renown for having odd color tints instead of being a true neutral density. Not sure about their other line of filters.

definitely agree, I have some of their nd filters and they've definitely got a brown tinge to them. They do however make for a nice old-style picture...

That made me lol

I guess I have more research to do.

Lee or Hi-Tech. Unless you want to pay $250 a piece for the entry level Singh-Ray ones. Personally, I like what Lee has going on with their filters. Cokin sucks for ND and GND. The filters aren't truly neutral and will give your images a magenta cast. Singh-Ray are arguably the best you can get but expensive. The Lee filters are nice, but most companies make their filters out of resin so you have to take extra special care of them. I believe that Tiffen is the only company right now that has a steady catalog of glass based filters but they are pretty costly too compared to the other ones when it comes to quality.