New and eager to learn!!!

Hi, my name is Kasey. I recently had a very close friend pass who owned a couple tanks. He wanted to set them up but never had the time. So now I have them. I want to set one up for now until I get the hang of things. It is a 44 gallon pentagon tank, I have a bunch of rock, a couple circulation pumps, and some lighting that I think is too small for the tank. Can anyone help me with what else I need to get and any helpful hints along the way. Like do I really need a protein skimmer? Not really wanting to get into the real sensitive fish or corals. Also is it really worth buying saltwater for water changes instead of making it in house? Lots more questions, and all information helps. Like I said I am very new to this and do not like to just jump into things without having a strong understanding of them. Thanks