welcome to the forum
i would recommend adding your location to your profile to make conversation easier and more helpful
I'd like to start creating a bonsai, so I chose a creeping rosemary ... I've got to start somewhere instead of looking at the beautiful photos of other people's achievements.
i would recommend visiting local bonsai nurseries, to find out what types of plants people are using in your area. beginner workshops and courses often include a tree. if you're going to start
somewhere, that's where i would start. i would complement that with online learning (this forum, mirai videos, boon videos, bjorn videos, peter chan videos, etc.). fully immerse yourself, and start absorbing
a type of tree that is commonly used for bonsai will be easier to begin your journey with (maple, pine, juniper, for example), because answers to your questions will be easy to find. creeping rosemary (why creeping?) will be difficult to learn from, and will only slow you down!