At 18 I would start with 1 spray of Ammo since your NONE production is already fairly high. None of these are actually going to do all the work for you and aren’t necessarily going to make girls approach you either it all depends on the girl, if she is out going and gets a wiff of the Ammo then she might approach you. 90% is going to have to be you the pheros just help with the other 10%, Ammo should give you a confident feeling as well so that might help you with your shyness a bit.
I would do some IO, IS, and Ammo, it’s a good mix and the IO will make people around you more chatty and probably even yourself. The IS just makes people feel good and happy then the Ammo will add to all that so you get a kind of sexy vibe but in an intimidating way but more social sexy.
Check out this link on how to tell if a girl is interested if you get a couple of these from a girl while wearing it at a party, mall, club etc you should be good to approach with out worrying about getting turned down.
How to tell a Woman Is Interested in you. IOI list
Here is one that I recommend you read it will help you out a ton at first.