The dr tim ammonium chloride.
For Fish:
I always recommend a pair of clowns to start. They have some awesome colors, are pretty much always tank bred so they are extremely hardy. There are a lot of options like Wrasses, Goby (Need a lid for sure lol), Cardinal Fish, Dottybacks (can be aggressive, orchids have many positive reviews tho), or firefisd (also definitely need a lid). I would actually always recommend a lid as all fish can jump out of the tank and it may help with some evaporation. I got my lid from Kracken (which is pricey) although I have heard many positive reviews. You may be able to do some DIY with some mesh too. Just be careful about covering it entirely with Glass as you can cook the fish, don't DIY glass lids lol.
For Corals:
Honestly the key is not too rush it. I honestly would start with some soft corals since they do not rely on managing the parameters as much for alkalinity, magnesium, & calcium. LPS and SPS corals like Hammers, Torches have skeletons and they are expensive and can die if parameters shift too much. Before trying those I would recommend a Duncan coral as they are less expensive and similar difficulty. Do you have test kits to check these parameters (API can be not too reliable as well like Ammonia always showing 0.25). If you get a LPS or SPS you will have to keep up with regular water changes and possibly (likely) even dosing. That is not to say its a bad thing but I honestly recommend sticking to soft corals for at least a month (if not more) to kind of get the hang of it and some of them even look better than the hard corals in my opinion (lol) Learn how to test for alkalinity, magnesium, & calcium. Do you also have a refractometer for measuring salinity? It is very disheartening and expensive to spend $200 and the coral shrivels up and dies quickly because of a small thing you missed which you likely will learn in the first month of doing tests (weekly etc).
It sounds like you light the long flowy look so I would recommend Neon Green Hairy Mushroom. They don't have as long as tentacles but they do have that kind of flow and are a soft coral. Very Hardy
Another very easy one (but definitely needs to be isolated on an island or on a back wall) Is Green star polyp. Now some people may say to avoid this but it honestly looks awesome on a back wall and is rather difficult to kill. It also is a great indicator coral to tell if the parameters are off in the tank. I have some on an Island and on the back wall of my tank and it looks awesome.
Another great one (although it will likely need to be isolated) is pulsing xenia. If you like active corals with a lot of movement these guys are great. They do grow like weeds (like GSP) so definitely want them on an island or to just keep them in check but if you google them pulsing its really mesmerizing. (DEFINITELY GOOGLE A VIDEO as the photo does them no justice lol)
The last big one is Zoas, they are much more tame then the other two but they grow quickly are pretty much any color you want and are hardy. You can also create a Zoa garden and mix and match them! Example: