How do you make gradients so well, without getting the tips dirty with other colors? 
well, the tips get a bit dirty as well when you blend, but somehow it does not reflect on the next stroke. It really depends on which brand you pick(?) Don't take my word for it cuz I'm such a rookie on this, but I only tried 2 brands, and promarker was the better one in my opinion.
I will remember this. Thank you for your reply!