Hehe the first step is getting used to the English saddle. People find it completely different than a western saddle, so get used to Blu's gaits in an english saddle :)
Secondly, to help you jumping the following will help:
- collection and extension FOR SURE
- leg yields and lateral movements (haunches in/out, shoulder in/out, travers, renvers - but the last 2 are higher level movements)
- good circles will always be your friend.
Those are some very BASIC movements that will help your jumping in the long run..
I always say that all (high level) jumpers are high-level dressage horses, but not necessarily the other way around :)
All the "big" jumpers need to know higher-level dressage or they wouldn't be able to do the things they do to get around the course.
Good on you for taking up dressage for your jumping, that makes me SO happy and proud of you!!