Hi,
I'm new as well, so can give you my thoughts. If you do not have time to read all the below my advice is to start small and gradually build bigger tanks until you reach your goal. Smaller tanks are easier to manage. You can always sell or upgrade your setup along the way.
The types of criters you want will decide the aquarium setup you will need (how big and how advanced). There are three basic questions you need to answer before starting to plan entering the hobby:
Do you want a fish tank, o coral tank or mixed?
Do you have room & funds to have a large setup or not (again depending on the requirements of the fish/coral)
How much time you want to dedicate to the hobby
What you plan to keep inside: larger / multiple fish will dictate a bigger tank. Tangs are large fish so you will need a large tank with a sump and strong filtration both mechanical and bilogical. Smaller fish, coral only can go nano 10-20g and even below.
Size: there is always a trade-off between size and stability (and equipment). I've seen coral only nano tanks with minimal setup. You cannot get away with this if you have a large tank.
I have a 30L nano tank. At this size the running costs are very very low. I buy rodi water do not need a rodi setup. I can easily restart the tank in one day if it crashes, including cleaning, new sand new rocks etc. Trade-off is I need to check it often ...if something dies, the water quality can be affected quickly. Larger aquariums need lots of sand, live rock. Larger more powerful multiple lights. Stronger filtration, multiple powerheads. Sump is a must. Most likely rodi filter as you will need a lot of water. Changing 10% of water weekly is costly as you need a lot of salt.
The time: this is a tricky one. Smaller tanks require less time to set up, less time to change water but require you to spend more time on checking parameters. Large tanks require a lot of initial time but are more forgiving if something is not working well due to larger volume of water.