So if anyone can point me in the right direction I would greatly appreciate it. Thanks a lot.
The right direction (I think) is to try stuff before you buy anything;
Look into getting mask, fins and wetsuit first. I don't know if you use snorkel but if you do get that also (I have one and take it with me to the site but not on the dive usually).
These are easyest to get out of the way. For mask the best mask is the one that fits you best.
For fins ... split fins are good for low effort with flutter kick, but in my opinion you can get even less effort for the same speed with a good frog kick (it will take some time to get the frog kick and you definitely cannot do it with split fins).
For regulator ... it depends on the price range, but everyone who tried them seems to swear by apeks and scubapro ( I usually swear by my cressi ellipse

). You should definitely try the regulator before you buy it and check that you can get air confortably using it, especially in an head down position and face up (on your back) underwater. Some regulators tend to let water in in these positions.
You coulf also decide if you will go for nitrox later (it makes no sense in having to replace your reg in 6 months time).
For BC ... here is a bit tricky (everybody seems to recommend something else). I'd say
not to go for the Mares HUB (do a search on the board if you want to see why).
If available in your area, try to rent different styles (jacket, back-inflated, and backplate+wing) before you decide.
For BCD, I'd look first at confort underwater (and body position - you don't want to have to make a continuous effort for maitaining your position in the water) and at the surface; Then I'd look for clipping points (D-rings) to be in accessible places, then for any pockets it might have.
Weight integration might also be something to look for. Mine is weight integrated, but lately I just keep using a weight belt and not the integrated pockets (it's just a personal prefference). I use a TrippleL Orion (or ScubaL Orion I think); Lastly, it should be pink to scare the fishes away

.
For your sister, she could try some women's BCD models (I don't know the difference for women) or a BP (I heard they can be infinitely adjustable ... or something

).
Anyway, choose your gear with the mindset that it's yours for life; If you don't abuse it ( much

) it should last for more than five years.
Also, serviceability in your area could be an important issue. Yopu don't want to have to ship your gear over half the world for servicing.