license
It would definitly be a wiser move to go straight for the B license, you do 85-90% of the work doing the A license syllabus then you have to go over it all again to do the B.
Also dont forget you will automatically get an A license when you complete the B.
I also wouldnt be so dismissive about not getting a position with an airline unless you have a license. There are many companies out there who employ unlicensed mechanics especially in base maintenance, where in my opinion you will learn a lot more about aircraft maintenance and gain the relevant experience for your license. Then you would be in a better position to get employment out on the Line.
The license isnt everything for someone at your age as you cant even hold an A license till you turn 18 anyhow. If i were you I would try and get some on the job experience somewhere maybe even at weekends/evenings just for starters.