First off, let me say that I am still a newbie, but I recently went through your same scenario.
Be careful buying on craigslist. A lot of the stuff isn't a deal once you factor in the cost to service the regulators. Plus, if you aren't familiar with the equipment and don't have the time to research everything, you might be buying something that is really old, discontinued, not serviceable, potentially dangerous, etc. Not to scare you away, just make sure you do your research or have someone helping you that knows their stuff. That being said, sometimes you can find some really good deals on craigslist. Since I started diving 2 years ago I have purchased 3 regulators off craigslist that were brand new, never used, for pennies on the dollar. Kept one, and sold the other 2 on ebay for double what I paid.
Regulators - I'd recommend sticking with the name brand companies (scubapro, mares, oceanic, aqualung, apeks, zeagle, etc). Look for something that is in good shape, not to old, and recently serviced (with receipt for proof). Don't get caught up in all the extra bells and whistles that some regulators may have. I believe in keeping it simple. Often the simpler regs are cheaper so people think they aren't good performers (this is where doing your research comes in). If it hasn't been serviced than factor service cost into your purchase price (anywhere from $80-$120 to service 1st, both 2nds, and gauges). You are usually better off buying a complete regulator setup (dollar wise), than piecing a set together.
I personally went with Mares Abyss for my reg set because it's a simple design that has been around for years and years, and it's an all metal reg so I don't get dry mouth as bad. It doesn't have any adjustment nobs, but I don't really think I need them. In the 2 years since I got certified I've dived sherwood regs, scubapro (low end to high end), oceanic, aqualung, Mares. To be honest, I haven't really seen much difference from one to the next except for the dry mouth previously mentioned. For recreational diving they have all performed.
BCD - Do you like the jacket style? Personally, I don't like it because it makes me feel squished, confined, uncomfortable, etc. I was certified in jacket style and this is generally what you will be rented on dive boats. Your other options are back-inflate and backplate/wing. I really like the bp/w setup, but you may not. It's a personal thing. I like to take a minimalist approach, and be as stream-lined as possible.
My first BCD was a Tusa Jacket style (don't remember the model). I quickly got tired of the squeeze, and I didn't really find it comfortable. After talking with an ex-combat diver at work (one of the guy that actually stood up the USMC combat diving school in panama city), I decided to look for a back-inflate bc based on his recommendation. I ended up with a Zeagle Ranger. It is a great BCD, very comfortable, very robust, but it was a little bulky and a little much for my style of diving (single tank, recreational dives). I decided to get a slimmer back-inflate BCD. So I sold the Zeagle and got an Oceanic Exursion. It was a good BC, but I just didn't fall in love with it. I didn't feel like it fit me just right even though it was properly sized, and I still felt like I just had too much gear on. One thing I noticed with back-inflate is that it tends to push you face forward when floating on the surface if you're used to jacket style. To compensate for this , distribute some of your weight to the back trim pockets or lean back slightly or both.
So finally, after hours and hours of research on scubaboard/online/etc I decided bp/w was the way to go. So I sold the excursion and I got a SS bp, and an oxycheq wing. It was simple, it was comfortable. I was really excited about it just wearing it around the house. Once I got it in the water I liked it even more. No more shifting bcd/tank when i turned/rolled etc. No more bulky gear. The tank seemed fused to my back. I felt like I was snorkeling. No weight belts or weight integrated pockets needed as I didn't need extra weight anymore. Trim was improved, and overall diving was more enjoyable.
My gf recently got certified and since she is just starting out I picked her up a jacket style BCD on craigslist. Used only a couple of times because the lady had an inner ear problem and couldn't continue her certification. It was $75. A good deal for sure. I think jacket style is good for beginners because beginners are usually very awkward in the water, and on the surface it keeps you heads up without you even trying, plus I think people feel safer in them because they are like a life jacket.
My gf is also small like you at 5' and 100lbs. We found the womens small oceanic isla fits her well. She wears a size 5.5 shoe, so finding her fins were a little more difficult, but I picked up some small force fins that fit well with a neoprene sock. Speaking of force fins... The way you slip them on and go (assuming you have bungee straps which you can make for $6 or buy for $35), it really feels like you are barefoot swimming.
, but I didn't own anything "new" until I started working for a shop. Not everything you see on craigslist, ebay, and this board are going to be deals, but a lot of it really is, and you can end up with some really nice stuff! Buying stuff this way, you can't be under the expectation that you're going to get everything immediately like you could if you bought it new. Let other people spend way too much on new gear and then buy it from them at a great price when they decide diving isn't for them a week later 
