That's a tough one. I used to have an oily T-zone...it's cleared up a lot, but it took time. The routine that I followed to combat it is one I still used today with a bit of variation throughout the year as my skin changes a bit with the weather.
So I start out with cleansing. I use cetaphil (or the drugstore equivalent which is the same formula, just less expensive). What I do next depends on whether or not my skin is oily. If it is, I put in a couple of drops of witch hazel on a cotton ball and gently wipe my t-zone. If it's not, I skip ahead and use a light moisturizer, usually something with a minimum of SPF 30 (Eucerin makes a good sensitive skin, non-oily brand) during the daytime and aloe vera gel or coconut oil before I go to bed.
Once a week, I mix in a bit of brown sugar into the cetaphil and gently exfoliate my skin, doing a little extra on the T-zone. If things are especially oily, then instead of the brown sugar scrub, I use Clean and Clear's Blackhead Clearing Scrub. I don't know if it actually works for blackheads since I use it for combating oiliness.
This is what works for me. It may or may not work for you...do a patch test with the clean and clear and the witch hazel to make sure your skin won't react badly. And most importantly, if you're having a hard time figuring out what to do, speak to a dermatologist.