What is it about ABDL that even interests you in the first place?
Not all ABDL are fully ABDL, some lean more towards the DL side or more the AB side. Some like to play with toys, some do not. Definitely don't spend money unless you're sure you want something.
Define exactly how and what you need to hide. If you live with an SO you don't want to come out to or are still at home with family (who you probably SHOULDN'T come out to) that can change things up.
I personally have a small safe that I keep my ABDL stuff (including my intentionally small diaper stash) in. This may or may not be practical depending on your living circumstances (parents can be nosy AF even if you're a legal adult) but if you're already working, can be easily explained away as a place you're keeping your financial/personal records safe in.
As for good diapers, a lot of vendors sell sample packs and that's the way to go at first to try out a bunch of different diapers. I personally like abuniverse and rearz a lot. Rearz has the convenience of easy accessibility and with fulfillment by Amazon you can either send to an Amazon box for discrete pickup or just arrange to have delivery on a day you will be home so you don't have to worry about someone intercepting your package.
For disposal, I like grey or black garbage bags that are scented (chlorox is good if you're not sensitive to bleach but they have other stuff as well). This controls odors so if you have to hold onto the used diapers for a few days until you can dispose of them discretely, you don't have to worry about your room smelling.
For learning how to diaper yourself, there are actually pretty good videos on YouTube and the like.
