I'll go against the grain on this one! Small tanks are hard to keep stable chemistry wise, I usually would recommend a 75 for a first timer. Given your experience maybe a 40 breeder would work for you, I would start out no smaller. Also a sump helps increase volume and provides stability, as well as a way to hide heaters and the skimmer, and some of the rock if you want a minimalist look in the tank. Agree that heaters (use 2 of half the required wattage instead of one large one), skimmer, powerheads and lights are what you need. I also subscribe to the pound per gallon rock guideline, make your sand less than an inch or over 3 inches IMO. Lastly don't put nems in a new tank, I would wait 12 months personally. Bubble tips are a nice first nem to try, but be aware that many clowns, especially when captive bred, will show no interest in living in any anemone. Good luck and keep us posted!