Well, ...the ideal paper for watercolor is watercolor paper!!
I use my 140 lbs/coldpress paper when I need to draw a real watercolor picture, the type of picture that cannot edited in computer.

BUT since I'm quite poor artist -_-" so it'll take high cost if I draw all the pic in real watercolor paper, so whenever I painted picture that can edited in Photoshop later, I'll use normal A4 paper....which is very thin and easily torn, and watercolor dry as soon as it touch paper surface, hard to controlled the color spreading, etc---all are bad things.

Another bad thing is all my picture painted on A4 won't worth like the one painted on watercolour paper, it's just a piece of worthless junk paper.. -_-"

So I don't recommend it!!!! This is forbidden for you!!
When I studied watercolor (8 years ago) I also use real watercolor paper, and you should too!

--------------------------------------
As I said before that watercolour need to wait & patience, that's about layer painting.
But if you want gradient in your picture, you must be VERY QUICK.

-Prepare the colour you need in the palette, and checked if they're too wet or too dry or not.
-After you paint one colour on the paper, quickly wash the brush in clear water, and pick another colour and paint quickly! (or in case if you're lazy, just pick another colour in the palette without washing you brush first : )

Watercolor dry very quickly and you must be quicker! or else you'll find yourself painting on colour that have ugly 'edge'.

...Hmmmm...do you understand?