Well,... you already had a gf, so it's not like you are clueless. You don't necessarily need to be that good at flirting. Already being interested in someone is a good start, if you have that then it's just a matter of spending time with that person.

Maybe you also need to let the matter of your previous relationship go. If you are a bitter person, nobody will be attracted to you. This being said, the best way to get past that IS actually to get a new gf, so it's a bit of a catch-22.