I also wanted an Emerald Tree Boa as my first snake, because they are really beautiful, but I am so glad now that I didn't - all those who keep them say that they are not good snakes for handling - and if the snake doesn't like to be handled, it will stress out and you won't like it either!
So, I think you are being very realistic, and doing the right thing by asking for advice. Everyone's will be different, but here is mine:
I did start with a ratsnake and a corn snake, and actually really enjoyed them and would have them again in the future. There are some really spectacular coloured cornsnakes out there, and they get pretty big in time.
However, I think you can't go wrong with a standard Boa - there are plenty of options as to pattern and colouration, there are plenty of responsible beeders and sellers on here who can guide you to a great snake without it costing a fortune, they get big but not too big, they have character and a great temperament for regular handling.
Some people will guide you towards Ball Pythons, and there are every many of those around, but in my opinion they aren't too much fun to handle - a Boa is more responsive to its owner (Now I'm going to be shouted at by Ball Python lovers, but I did say this was a matter of opinion
).
I'd also go to your local pet store and see what kind of support there is in the area - get an address for a local reptile vet, food stores etc. You're going to need frozen mice to start with and rats later on.
Hope you have fun choosing - let us know what you get!.
