although I've owned this game for quite some time and watching a lot of casts, I actually don't play that often. So I know my abilities are limited

I was playing against Ostheer and was doing okay, got most of the map most of the time. (okay I lost my Stuart in a stupid way, was not paying attention) But then the opponent got a ostwind and started blobbing and I couldn't handle that.
Any tips? Even basics