I think the best way you can go about it is with moderation. Research your curiosities; ask questions, look things up, observe. It's okay to make a rare impulse purchase, resist shopping binges. It's best explored over time; once you discover something works, you can buy in modest quality, be it binkies, clothing, even a type of toy. It takes time for your little side to develop, don't let the shopping outpace your development.
Along the way, your feelings will change: how you mentally expand into the journey, how much you expand...finding a limit that works when you reconcile both your AB life and adult life; even your partner's comfort level in this regarding their involvement. This is life; development takes a lifetime, even AB does, so the more you evenly pace this with your vanilla life, the better the two will coincide..."mesh", if you will. Don't accelerate or force anything...grow steadily.
I've omitted diapers because that's all about money & taste; plus, diapers come and go. You'll eventually find what works for you there.
Oh...and if your mate decides to join in, at any degree, spoil them; it can be a hard job, a tough journey for them. Help them clean up after you...and love 'em like nothing else matters because having a partner in this is, as you can and may have already deduced, worth ten times its weight in gold. Parenthood is tough...even tougher for a parental of a big baby doing big-diaper changes and other big-baby care.
Focus on your vanilla life and big-baby life equally...and remember: vanilla life has right-of-way because of the Adult part of the Adult Baby. Other mitigating factors will enforce that notion, such as life-demands, an overstressed partner, money (of course)...if you find yourself increasingly running away from responsibility, a problem exists. Ya can't run from responsibility.
Most importantly: keep talking. We'd love to learn from you as much as you may learn from us. That's your biggest asset: community & sharing. Time is all we all have; use it wisely.
And don't forget to have fun along the way! 🥳