I guess there must be plenty because I've always been tall and trim and I've done well with women every time I've put myself out there.
Get regular exercise 60mim x 5 days a week. Plenty of cardio with core and weight work. Nothing complicated. Just enough to tone muscles and burn off a little fat. It improves your confidence and gives you the charge you need to be desirable.
Don't bother trying to build up muscle mass. From the way you describe it, no amount of training would put bulk on your body type. Dress sharply instead.
There are lots of places you can go for seduction advice. But I have only focused on looking good, body language, being interesting (without being obnoxious), and being direct. I found this book on body language to be helpful (not pua) http://www.amazon.com/Love-Signals-Practical-Language-Courtship/dp/0312315066
It helps to be your best self, but you don't need to become someone else to get women interested in you;
This book, although not about game, turned tings around for me completely: http://www.amazon.com/Love-Signals-Practical-Language-Courtship/dp/0312315066
It's a short book on body language that explains how to read a room and the people in it, explains which women might be interested (and which are not), provides guidance on how to get women to develop an interest in you and so on.
It's not about scoring but I found it fascinating and it helped me hookup a number of times. I met a few great ladies by following some of the tips.
the first step is getting out of the house. treat everything you do as practice. at some later point when your life is more settled you can move on to playing for keeps.