I backed into bonsai by growing sticks in pots. Welcome to the club carol.
Can you train up a fire thorn? (Tom is pushing a PM to an open forum) Yes, yes you can. if it has a failing, it is because it too sounds like another 'stick inna pot'. I won't tell you not go grow sticks. But will urge you to go on search for a stump of heroic proportion.
One big enough to flip a stolen shopping cart over as you load it.
If your library and tool bundle are well started and
you are collecting soil specific to bonsai. IMO you'll be well under way.