Enjoy your promarkers Rosy
I would also recommend a Memento inkpad. Cardwise start with what you have already and see how well it works. It you find its no good then another good card is the craftwork cards digital cardstock There are lots of other types that are equally as good though Basically stcik to a mid weight (maybe between 160 -250gsm) and the smoother the better though beware of some coated card as I ve had some that really "grab" the ink from your promarker (to the point that the pen will dry up)
Phrees kind comments make me blush:blush: but there is not great secret other than lots of practice and reading tutorials. I tend to find cards that I think have been really well coloured and then go to that persons blog. More often than not they will list the colours used and often show you how they acheive their shading. Its then just a case of giving it a go. Oh and dont get disheartened if it doesnt turn out how you hoped I spent over 2 hours today colouring up an image just to end up ruining it at the end when I was shading the hair and got a bit carried away It ended up in the bin :giggle: