When you say you have a community tank and you want to move on to a reef I assume you mean a saltwater community tank? Regardless, read everything you can get your hands on or eyes on online and research, research, and research some more. Make sure whatever you read is from a reputable source, there is probably more untrue, outdated, and just plain bad information than good.
The easiest way to start a nano is to buy a 10 gallon or a 20 gallon long, purchase a Maxijet 900 or two, buy a small 50-100 watt titanium heater, some live rock, some pure aragonite sand or live sand, a decent lighting setup, salt mix and RO/DI water and get it up and running. The all-in-one nano tanks are not truly all-in-one. Many have design flaws that need modified; they are not plug and play. For less money, a small inexpensive glass tank can be turned into a beautiful nano. However, if you like the design of the all-in-one tanks and do not mind doing some modifications they still make great tanks!
:joy: