My girlfriend started in goal a year ago after skating out for about 5 years, she enjoyed it but always wanted to play goalie so after saving up she got her gear. As far as playing goes she loves it and doesn't even consider changing back to skating out. When she got her skates she spent a few weeks just skating on them at public sessions and getting used to the differences. She had also spent about 6 months strengthening her legs and core as well as stretching to increase her flexibility. As far as gear goes she bought all new stuff just because she is rather particular about her gear and also figured the investment of so much money would motivate her to stick with it if she got discouraged when playing initially.
Biggest advice I can give with the gear is if you want to get used that's perfectly fine, but make sure you're helmet is good quality and fits well. Pucks to the mask are no joke. Also look at clearance gear if you want if you wait until the new years gear comes out you can find some sweet deals. My girlfriend was able to find top end skates for less than 200 and a pro level chest protector or 250.
For women there really isn't much you can do for fit. Usually intermediate sizes work well, but my gf went with a senior small chest rig so she could get the pro level pads. It's not ideal but unless you get custom pads made you're kind of stuck. Best option is to try on everything if you can and find what works best for you. If that's not an option do your best to find the right size and then play around with the straps to get the best fit possible.
Last note is invest in some good knee pads, it may not seem to bad on the knees but the constant dropping does take a toll on them so better to save them for the long run.