I think you may not be getting as much feedback on this simply because there are a zillion directions you could go with this.

If you look on deviantArt and just do a search using "Colored Pens" you see a huge variety of looks and styles.

If it was me, I would probably attempt something incorporating watercolor paints (which are cheap) but that's just because I'm on a watercolor tear these days.

A lot depends on the look you are after too. A lot of people use those Prismacolor pencils, although I think they also do pens but I don't have a lot of experience with pens. You can go with dipped ink pens as well and buy vials of colored inks to use. Then there are the markers as well. The list goes on and on.

I'm thinking if you can find a look you like, you might see if you can find out what the artist uses and that might give you an indication.

As far as a large page to work on goes, I would hit up your local art supply and check out what they have. Everything from thick watercolor paper to hard poster board I'm sure. Look for a surface you want to work on based on the feel of it, etc.

Sorry I'm not more helpful