My advice for INTP's who suck dating is to make more friends of the opposite sex because a couple of them are bound to crush on you. You are already comfortable with them and it's cool to start dating since the only reason you became friends is to date them.
I say this because the couple of more serious relationships I've had all started out as friendships first, so they had already borne witness to my somewhat awkward ways and at that point found it endearing.
Don't worry about your late start because I think we all started a little later than our peers. I know I did. And if you are gonna keep with the online dating remember to actually go out with them (in person) after the first couple of messages or else whats the point?