Hi C152pilot,
You require a PPL (which I assume you do) and build up your hours to 150 hours total time (100 P1). During this time study for and pass the 14 ATPL Written Examinations.
After they are complete you can undergo the JAA CPL Flight Training course and Skills Test. Once you have your JAA CPL go and do your JAA IR course.
This will give you a JAA CPL/IR with ATPL Subjects Passed which some (if not most) people call a frozen ATPL which doesn't really exist.
You will probably require a MCC course certificate as well before an airline will employ you.
So once you have that lot you can apply to the airlines for your first position.
If you don't get any success you may decide to go and pay for your own Type Rating training. Again I don't like the term "buy a type rating" as you're not buying but paying your way through the training - you could still fail the training (either the ground exams or skills tests)!!!
So the answer to your question, "should i get an IF rating and build up my hours" is yes you have to go and obtain an Instrument Rating (not IMC) and a Commercial Pilots Licence before an airline will even look at you.
All the best.
Charlie Zulu
PS: Apologies if I have come across a little sharp, I'm very tired after a 12 hour working night, off to sleep in half an hour, wow!