Tuners...I use those $20 black Korg tuners and love them. Some people like rackmount tuners because you can see them easier, but I prefer the cheap stuff as long as it works well.
Active input vs. passive...the active input is usually turned down compared to the passive input. You don't have to use the active input on an active bass, BTW...I use a passive input on active basses all the time because I don't want a signal cut.
There is often a tuner out on most amps. If you don't have one, you can do what I do, and that's yank out the cord from the amp and plug it into your tuner real quick
If you have a bass and amp and tuner, that's all the equipment you need to gig, however, some people do like to plug effects up to it. I'd say if you're playing metal or hard rock, a distortion would be a cool thing to own.