Hi olle,
Finance-based Programs often put a greater emphasis on an applicant's Quant Scaled Score (sometimes more than the emphasis that they might place on the Overall Score). As such, scoring at a much higher level in the Quant section would likely benefit your applications a great deal. That having been said, you've also listed some highly competitive Schools, so you can't focus solely on the Quant section - as there will almost certainly be a block of applicants who score at a high level in all sections (and you don't want to 'look bad' by comparison).
When it comes to studying for the GMAT, there are a variety of different options. Most GMAT Companies offer some type of free materials (practice problems, Trial Accounts, videos, etc.) that you can use to 'test out' a product before you buy it. We have a variety of those resources at our website (
www.empowergmat.com). I suggest that you take advantage of all of them then choose the one that best matches your personality, timeline and budget.
If you have any additional questions, then you can feel free to contact me directly.
GMAT assassins aren't born, they're made,
Rich