Welcome ...
I just picked up a Lumia 635, to substitute for my Lumia 1520 (it's needing service, but that's another story).
As someone who's had a few Windows phones (Lumia 920 now my wife's, Lumia 1520 luv that phone, now Lumia 635 temporarily), I'd suggest you try the device for the OS experience. If you like, step up to a better device & enjoy all that Windows Phone has to offer.
Check out MyAppFree for deals on FREE (or reduced price apps), register for Bing rewards & earn points towards Store credits, Amazon gift cards, etc and stay tuned on Windows Central for FREE app offers. Almost all of my paid apps were either purchased w Store Credit (earned thru Bing) or d/l when they were offered FREE. The Lumia 635 appears to be a good entry point, even though it's only 8GB onboard storage, it takes an (up to 128GB) sdCard for addon storage. Don't judge the camera on the Lumia 635 (it's not the best), the Lumia 1520 has one of the better cameras out there, along with the Lumia 1020.
Good Luck.