Toner is and isn't necessary... It helps to pull out dirt that may be under the skin, oil, and makeup that has not washed completely off. Some toners with alpha and beta hydroxy help to expholiate the skin... The thing with toners though is that they should be used but not left on the face. Wipe the face with a little toner on a cotton ball, let it sit on the face for a few minutes and then dab H20 on face to wash of excess toner and pat dry.
Be careful though--- don't get astrigents... they are not the same thing as toners and deplete your skin of oil causing your skin to produce more oil to counter the severe dryness of the astrigent.
BTW--- I recommend Neutragena's pore refining toner. It has alpha and beta hydroxy with glycolic acid and it is not too expensive.
Toners, I think, just make sure that you have all the dead cells and junk cleared off your face before you put on your acne meds or whatever. It's up to you whether to use one or not. They are particularly good if you wear makeup, but since you're a guy you might find they're not necessary.
Also, if your skin is really sensitive, I would advice against it unless you could find one that's VERY gentle like rose water or something. Most toners fall into the category of astringents and that can be very bad for people with acne. I have never been able to use toners even though I wear makeup because my skin is so sensitive and dries out so easily.
Just experiment. If you think a toner might help, give it a shot.