Hi Alberto86
I would advocate a FI course, I became so much more comfortable and confident with my own flying ablity after instructing and although it may be single engine piston, it really does bring up your level of handling. It will serve two purposes, it will increase your hours which can only be a good thing and it will allow you to network. Furthermore whilst gaining those hours you can keep your eyes open for air taxi work etc, because although Rickford suggests that the airlines like to recruit FI's, in my experience they much prefer commercial experience (or at least that's what all my rejection letters keep saying!) and an FI with commercial experience should be very tempting.
Good luck whichever way you go.