Nice! Adding your first corals! GSP is super hardy, and it won't spread unless it is touching another rock. I have it growing on the back of my all in one tank. It is doing great and looks beautiful! GSP does fine in a variety of lighting and flow. But make sure it gets a bit of flow so detritus doesn't settle on it. I would use a pipette once in a while to blow any debris off. Kenya trees and toadstools are really easy. Zoas too (some are finnicky for some reason, but 90% of the time beginners have good luck).
Mushrooms are also very easy. I'd recommend Discosomas or Rhodactis/Hairy Mushrooms. Hairy Mushrooms are really underrated! They grow large, sometimes fast, have extended tentacles, and sometimes host clownfish especially if they form a small colony.
As far as LPS corals I would recommend Frogspawn, Duncans, and Blastomussas. Blastos are super underrated, and hardy. Don't get ripped off though since some places charge ridiculous amounts for them. I would wait till adding LPS. I jumped ahead a bit with some corals without making sure some of the parameters were all good. But they really are not challenging if things are looking good.
Rock Flower Anemones are also pretty easy. Very hardy, and cool.
I would wait a little while until venturing into LPS and rock flowers though. It's better to be safe and wait a bit then pull the trigger quickly. Sometimes corals look great, but there may be a problem that makes the coral slowly get worse over time. Sometimes it is minor like it will be ticked off and won't open or loose color due to a small issue that can be easily solved. BUT sometimes it causes much larger issues and the coral is in bad shape.
Just make sure phosphates are at least below 0.15. Preferably below 0.1. And Alkalinity is relatively stable (which is a bigger deal when getting into stony corals).
ALSO DO NOT FEED CORALS FOR A WHILE. It is so unnecessary, and will put a lot of excess nutrients in the tank.
But if you love soft corals do not let anyone pressure you into LPS, and SPS. Full softy tanks often look great!
I personally have a mixed reef, and only have a couple easy to keep SPS, and I just happen to like them a lot.
Sorry I typed a lot. Hope all goes well. Message me or reply to this if you have any questions at all

I started my first ever aquarium for the first time last year (jumped straight into a reef tank).