Shrink a database below its initial size
As some people already mentioned you could create new database and "copy" stuff over from old database. This would be the best option for you. However I've noticed that you want to do it quite regularly. So your best option is Redgate Data Compare and Redgate Compare. Both are part of Redgate SqlToolbelt package. 

So what you do:


Create an empty DB with small initial size.
Use Redgate Compare to copy db structure, functions etc from old db
Use Redgate Data Compare to copy data from old database to new one
You work on dev database and then at any time you either do just Data Compare and update the Dev DB regularly, or if you do any changes to db you can deploy those changes using Redgate Compare and then doing Redgate Data Compare.


What is good with Data Compare is that after you copy those 30gb of data (you can do it starting with some tables only) after a while it just needs to 'recompare' only some changes and not whole 30gb of data. Which means it will do a lot less impact on both databases then it would by copying it normally.