You learned the most important thing early, my friend, you went out and sniffed and found three that your nose told you are really magic for you. Damn, apply the appropriate sports metaphor here, because whatever sport it is, you did the action that brings the biggest score.
Learning scents is as simple as one person sniffing many scents and letting one or a few take you. It's great to have found those three, and they're fine finds. I like Platinum Egoiste especially.
It's hard to find Chanel online for cheap. Sad but true, but unlike many of the large brands Chanel somehow keeps very tight control of the sale of its products and it's hard to find them cheap. If I knew of a place that has them cheap, I'd tell you, but I've got to warn you that I'm skeptical that you'll be able to find one.
It's a tough call about how much can be worn in a small office without being overpowering. Experience is the best and only reliable teacher. Try out the deodorant only on Monday and see how that goes. Try a spray of the edt the next day, and so on. Only your nose, your observations, and your co-workers can tell you. We don't know because we won't be there.
Trying your best is the best one can do. If you over do it remember, it's only a day. There is tomorrow and all the rest of the working days of your life and they'll be different and better because you'll be wary of making the mistake again.
Very best, and keep sniffing!