Nanos are the best way to go when first starting out imo. 5 gallons can go a long way with a little imagination.
See I say the complete opposite. Nanos are extremely hard to maintain stable water parameters. I've found out the larger the water volume the easier it is to maintain. When I had my 50 gallon I was constantly testing and checking parameters. Plus the fact I had to have chiller to keep the water temp in range. I was constantly loosing corals and fish do to the instability of the water. I never felt safe leaving my tank alone for a few days.
Then with my 180 gallon I felt that the temperature swings weren't as drastic and I ditch the chiller. I went to testing every other week cause the swings in parameters weren't as noticeable and I spent less time on maintenance.
Now with my 300 gallon I've only done 1 text in parameters this year and 2 water changes. The temp swing is only like 1 or 2 degrees between night and day. I really lose any corals or fish. I early spend anytime on maintaining, at most an hour a week and that's pushing it. My tank is running so well on auto pilot I feel it would b safe if I went on vacation for a week no problem, 2 or 3 if I had someone to come over and turn on my ro/di system once a week to fill up my auto top off drums. The only down fall to having a larger tank is the cost of keeping I running. I go through water filters quicker cause I use more water. Then it takes more electricity to run the tank properly.