Starting? Oh my. Well, I don't exactly know what to tell you. You've already kinda reached the most important milestone for starting.. knowing this is something you want to explore. Congrats new explorer of cute cuddliness!
The next parts are going to be up to you. What parts of being a sissy do you connect to the most? What kinda feelings are you wanting to play with? Giving a bit more detail about things is probably your best bet. If you're enjoying ABU Lavenders, you might enjoy other articles of clothing. There is all sorts of stores online that cater to this kinda thing, although I can't point you to any specifically.
If you have specific questions I would love to answer, but a lot of this is going to be about focusing on what you WANT as a sissy. There isn't particularly any one way to be one. You know.. other than the general fluffs and lace and ribbons and soft pinks, a big cuddly dolly and hair ribbons.
the best thing anyone could do is just find your comfort points and explore. Exploring can be scary and it can be fun. I have explored many different facets of my life over the years from Sexual orientation, gender identity, gender expression, kinks, hobbies and self gratification just to name a few. First don't think there is anything wrong with you, if you are comfortable with yourself and comfortable doing something try it again multiple times to see if it you or just a passing idea.
Be happy with you and you will discover why you are happy being, be it a sissy, AB, furry or whatever. enjoy and live.
I am sure there are many here who have good ideas of thing for you to try if you are stuck, but it is up to you to decide where you want to go. As for toys and thing see if it is something you like, start small or inexpensively and work up. you never know.
Hope you enjoy your self exploration and hope you have a lot of fun alone the way.