FF
I can only answer you from the view point of an instructor. I qualified three years ago this month and after 6 months in the doldrums undertook the FI course. You will benefit immensely from both the FI course and then the flying to follow, you are PIC and the decisions rest squarely on your shoulders, building experience and handling skills along the way. As an aside if you chose your place of employment with a little care many contacts can be built along the way.
In my case, I'm now 43!! With around 1100 hrs, my position as an instructor put me into the right hand seat flying with a company that requires a second pilot flying various piston and turbo prop twins in a commercial environment. I believe this to be a natural lead in to a F/O position with the experience gained and now feel well prepared for a multi crew position.
As to the type rating argument and I have at times thought of going down that route, the advice given to me ranged from, the positive "go for it, it gave me my first break" to "if you are going to do it, you will need to include 100 hours on line to make you employable" and from people in the know “don’t bother, wait till your employer pays for the rating" given my situation, I have decided against going down this route, as is said here there is no guarantee.
Ask 50 people their opinion and you will get many and varied answers, those that it has worked for (there are many who it hasn't) will say go for it. Some will say you need 100 hours on type, if you can afford £30,000 and can risk gambling that amount go for it. If you can survive on an instructor wage I'd say get the experience, build a few hours, network like mad, fly some twins, do your apprenticeship, you will be a more balanced and experienced pilot when you get that multi crew position.
Feel free to PM me with any questions and good luck which ever path you choose to follow.
FF