I know this is a very elementary question, but please be gentle. A couple of years back I bought a bike off craigslist for commuting to work/school. I used it for several months, but then my wife moved 800 miles away (with most of our possessions, including my bike) while I spent the intervening time between then and now finishing up my degree. Anyway, I've now moved to join her and want to get back to using my bike to commute.

The reason that I posted here is that the person I bought my bike from had taken a mountain bike, thrown slicks, fenders, drop-in bars on it, and moved the shifters to the stem (which I complemented by adding a rack and lights). So anyway, this dude just used some nylon strapping to wrap part of the bars (not very comfortable) and I'm now wanting to put proper bar tape on the whole bars - including the part where the bar bends back in. Someone in the past said that I'd probably need an extra roll of bar tape to do it properly, but here comes the stupid part, when I order tape will one order be enough to do one set of normal bars or just a side of normal bars (i.e. do I need to order two rolls to do my bars or three)? Like I said, it's a dumb question, but any other advice anyone wants to throw a taping newb would be welcome as well. Thanks.

Also, gel or cork (or is that a personal preference thing)?

One should be enough.
I wrap an old tube on the curves of the bar, then cover with the bar tape.

Most of the time when you order handlebar tape, you get enough to cover a standard drop handlebar. If there's something you really like, order two sets to get complete coverage on your Drop-Ins. Some places allow ordering individual rolls, in which case you'll want 3 rolls: https://www.velo-orange.com/trclhata.html .

Here's your bars:

Even though it's a drop in bar one should be enough? Or one would normally be enough and I should go with 2? Maybe that whole extra length where the bar curves back toward the stem isn't as big of a deal as I'm making it out to be in my head.

So I guess it sort of varies then whether an order is one roll or one set?

Yep. Cloth tape can be gotten by the roll- 2 rolls covers a normal handlebar. Most gel and cork tapes come 2 rolls in a bag, enough for a normal taping job.

Thanks, I'm intrigued by 10 Wheels' idea of using an old tube as padding rather than just making greater overlap in the taping in parts I want more cushioning.

IMO: gel or cork "tape" will be enough. Plus, since you'll probably need two sets, you'll have lots of extra for overlap.

True...