I don't believe that Tommy was ever brought in on the plot. After all, he wasn't that type of guy, he wasn't pivotal or needed for the success of the plot, and Castellano was his uncle/cousin - he was blood family.

In fact, after the hit, the one commendable thing Gotti did was to have a heart to heart talk with Tommy and treated him with kid gloves out of respect.

As far as his "crew" goes, Tommy was elevated to and maintained a "capo" post, out of formality and respect for his surname and his dad, Carlo. He was given just a few men to oversee, and had a small crew. Because his real value to the borgata was his control of garment industry rackets for himself and on behalf of the Gambino Family.

And with the exception of two or three key aides/soldiers, he had a few another "associates" as part of him. Just enough to run around and help facilitate his garment interests.

Gotti later assigned him as the "capo" to oversee the family's Connecticuts rackets, which was a big mistake! It turned out that Tommy's only arrest stemmed from getting mucked up in Gotti's later indictment.

Had Gotti left Tommy alone (because he did not need, nor want, to "oversee" CT) he most probably would never have seen the inside of a jail cell.