Why do you look at beaded ones it there as specific reason? I'd suggest to start with something like the ones below:
Blush UR3 Anal Starter
or a silicone alternative:
To grow up I'd suggest:
Pure Skin Player jr
The silicone alternative is:
VIP Super Soft
Much more versatile, you can't really get good penetration form beaded toys. They are more a warmup toy and I guess more suitable for ladies then men. It is really good to try different toys to get a feeling what type of anal stimulation you really like.
I've started with the Triple Ripple
and I have to say that despite of a collection of around 20 toys I still like to use it now and then but it took me so long to get over the last bulb back then
But what I figured out that I like to warm up with this toy as it gradually increases its bulbs and once it's fully in I enjoy the stretching and the pressure on the prostate. So it was much easier for me to get the right toys later.