Couple videos below to get you pointed in the right direction. Beginner corals is sort of a interesting topic because if truth be told some of the beginner corals are actually the most widely sold. They are popular not just because they are beginners but because they are, well, popular. Popular could mean:
They grow fast
Affordable
Fill in the tank differently than other corals
Provide refuge and break fish chase
Coral movement based on flow
Utilize nutrients
And so on. So for me I don't look at them as beginner corals at all but rather corals that would serve a purpose for a tank's maturity and biotype. I like to think of reef tanks as simple as a bucket. I can have a soft coral bucket, a LPS bucket, and a SPS bucket. Each have different requirements for chemistry levels and lighting. Each bucket has a set of rules that will lead me to success. Rules for what I can keep coral wise, fish wise, nutrients, and lighting. Just on a simple level.
Each bucket will have a set of easier to keep corals through advanced. Same with fish. If I now add a fourth bucket and let us call that mixed reef (one which I try and keep soft, lps, and sps) the rules just got muddied and my beginner corals suddenly changed

Because keeping a mixed reef is all that much more challenging due to the overlap of nutrient, lighting and balance I need.
As noted some of these corals regardless of soft, lps, or sps can over take an aquarium because of how fast they can grow given the right conditions. Xenia for sure. GSP also. I've had a Hammer coral (LPS) over run my tank as did a single rose bubble tip anemone (one coral split so many times I peaked at 14 of them, had to give some away, and finally upgrade to a larger tank). So see, it isn't just Xenia

There are fast growing SPS frags also.
TL; DR - few videos below may or may not help. What does is probably picking a reef bio type that will peak your interest and start from there. Maybe a bucket will find you and give you a place to start.
All the best!