you will probably enjoy a larger tank better, they are easier to take care of, as for eaase, the larger the footprint(l x w), the better
for beginners, it is actually best to get a 75 to 125 rect., they are much more stable as far as h2o quality, and aren't too much to handle, bu tmost of us are also limited as far as budget and or space
Imo, i would look into a rect 75 to 125 and go as big as i could afford, bear in mind you are also gonna want to get enough lr and skimmer and circualtion good enough for your tank(lighting can be done slowly, as you get ready for inverts, you cn add more), now realize that you will also need more sand too, but sand is relatively inexpensive(it's mostly the lr and skimmer along with tank stand and light and hood which will cost)
another thing: consider whether or not you intend to use a sump, they are a great help, and can make your tank more viewable, by putting your heater and some powerheads and skimmer in it, anyhow, if you are considering a sump, purchase it with the overflow built in, it's normally @50 to 100$ more, but is easier to maintain and won't loose it's prime, like a hang on can