Ok here is a list of things I would recommend buying as far as my experience with these things goes

WATERCOLOR PAPER

I would recommend Arches for the best quality if your doing high end commissions.
It's also nice becuase the single sheets of Arches are rather large. Keep in mind the heavier the weight the more expensive.
Example...(estimated prices)
140 Lb CP - $5.46 CAN
300 Lb CP - $15.95 CAN
It's also nice because I find it withstands the glue of tape rather well so you still get those crisp edge borders but the glue doesn't tear the paper. Trust me, you can have most amazing tape brand, but if the paper is lower grade, you have a higher chance of it tearing the paper.

TAPE FOR WATERCOLOR PAPER

I would recommend the Scotch Blue Painters Tape.
It's around medium tack unlike the green one so it doesn't tear the paper when pealing it off. Mind you, the quality of paper also determines if the tape will tear the paper as well as the weight. If it's screen printing paper or 90 lbs, you have a higher chance of it tearing as compared to watercolor paper that's 300 Lb.
Every single time I have ever used this tape, it has always given me a clean crisp edge.

MASKING FLUID / FRISKET

I would recommend the Dr. Ph. Martin's Frisket Mask Fluid.
Now I have the one with the eye dropper built into the lid but I would recommend the one without only because the eye dropper over time allows are in and all the masking fluid that's in the eye dropper eventually solidifies and becomes useless. Mind you the rest of the masking fluid in the jar is fine so if it's all you can find it's ok, but the eye dropper will eventually become useless.
It's amazing stuff. I have never had it dye the paper yellow what so ever after taking it off. I have left it on for days and never had any color change to the paper. It comes off easily and covers the area 100%. I have never had any leaks and I find it spreads very well.  I have also painted a picture and applied the masking fluid on top of the paint and peeled it off and it didn't ruin the painting under neath color wise or removing the pigment.

WATERPROOF PENS

I would recommend the Sakura Pigma Microns.
I have the joy of working in an art store and there for have been able to test over 50 different pens. And from that test the Sakura Pigma Microns were the best. They did not bleed what so ever. Once I put them to the paper, no amount of water or brush strokes across it would make it bleed. It's 100% permanent.
They come in many different sizes ranging from .500 to 3. Different styled tips as well as a range of colors.
They also come in sets, colored and black.

PROTECTIVE SPRAY

I would recommend the Krylon Matte Finish.
It's worked great for me. It is like most sprays so I do recommend spraying it out doors or in a well ventilated area. It's Permanent, Non-Yellowing, Moisture-Resistant, doesn't take long to dry. Also if your painting has glossy sheen in it, it will eliminate that.  I usually do around 2 coats.
Krylon is a pretty good brand so if you prefer ones with Gloss or UV Protection they are just as good as the Matte. ( I just prefer Matte )

WATERCOLOR BOOK

I would recommend Watercolor Moleskines .
I would buy out Moleskine if I could. I have 3 of these in the 5/8 size and 1 in the 3/5 size and will going to grab one of the largest sizes soon if I don't get it for my birthday .
I bring it with me everywhere. It's fantastic. The 5/8 fits in my purse and the 3/5 will fit in any guys pockets whether its jeans or a jacket.
It's pretty good paper, 140 Lb Cold Press. 72 pages (5/8).
I have used the Scotch Blue Painters Tape and the Dr.Ph.Martins Frisket on it and have had no problems with it.
I also like that it has an elastic on it, so after finishing a painting I can put the elastic band around it and it helps flatten out the pages.
I really recommend getting one. Just by having it I find I paint a lot more often since I can bring it every where with me and it's small enough that I'm not doing an overly large painting.

WATERCOLOR PAINTS

Ok there is quiet a few brands I recommend depending on the money you want to spend and what grade you want.

Student Grade -> Winsor and Newton Cotman Watercolors .
These are a great paint for student grade. I really enjoy them and find there is enough pigment in them to still give me the vibrant colors I desire.
These all come in Hue's for the more expensive colors. And some of them you have to use a bit more generously depending on the color ( ex. Raw Sienna ) to get more of a vibrant color to them. And then some you can use less and it goes a long way ( Paynes Grey ).

Artists Grade -> Winsor and Newton
and
Da Vinci
and
M. Graham .

I have found high pigment in all 3 brands and have enjoyed using them all. I'm not too picky really and will use a mixture of all 3 brands.

BRUSHES

Brushes are another one that's a bit harder.

If your looking for cheap student quality brands I would recommend the Curry's Brand 2500 Round Series.
They can only be bought through Curry's Art Store Online or In Store and they are only a Canadian Company.
I have never had a problem with the bristles falling out and they usually go back to their original shape. As far as holding water, they are ok. Nothing compared to Squirrel brushes but they do the job for the price they are. I enjoy having these with me for when I have my Travel Moleskine on hand.

Now if your looking for better quality brushes I would recommend the Escoda Watercolor Brushes Any Series .
These are a fantastic brand that holds more water and holds it's shape much better. You can get any series and and size and round/flat/filbert/liner and more. They are sold practically anywhere. They are rather expensive though and only go up in price the bigger they get.

If you are looking for a Mop Watercolor Brush, I would always recommend a natural Squirrel Hair Brush as they would always hold the most amount of water and give you what you are looking for. They are quiet pricey though, I know for example that a size 6 is $50.00 CAN.
If you want a cheaper substitute you can purchase a Camel Hair Large Round Brush for your Mop brush. But keep in mind, you pay for what you get. The bristles tend to fall out so I recommend washing the brush to being with before you start to try and get all the loose bristles out. And keep in mind, though it's called Camel Hair, it's most often Pony Hair or a mixture of many different hairs. But being natural, they make good Mop Brushes and will get the job done as well. I have a couple and now that all the loose bristles are out, it's perfectly fine.

True Natural Squirrel Hair Watercolor Brush.

Natural Camel(pony) Hair Watercolor Brushes.

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If you have any further questions or comments feel free to leave a comment down below