Welcome.
That is a huge subject.
Sounds like you are wanting to leave the security of the shop environment, get out into the big ugly world of "The Road Whore", and make "the big bucks".
If so... Just start by getting your resume out there to the staffing agencies and review the offers that come back.
As far as I know, there is no play book available for this. Every gig I've ever been on had different pay, experience/prerequisite requirements, and physical conditions.
Fist piece of advice is you do not always have to have all of the prerequisites to get a particular assignment. Those are often very flexible and represent "desired expertise" and not what they will settle for to get the project staffed.
For me, it has been a "School of Hard Knocks".
Take what gig you want, lean from it, develop a core group of contacts, mentors and friends. Even though it may not appear so, you will learn new things and every new gig Will fluff up the CV/ Resume.
Lastly, I've always said... "There are 2 kinds of people in this line of work. Those who travel and those who are BROKE!!!!".
Does that answer any questions?
If not, try to present a specific issue to respond to.