I have seen some very overweight garters ,or wannabe pythons :P.
You are basically choosing between very interestingly colored garter snakes ,often with more attitude than two corn snakes put together
.You can feed them many different things , fish(make sure you read the posts on fish as some are poisinous) ,worms,mice, various amphibians and more.Very active snakes and they dont become a handfull.
Lots of different variations.
Florida blue
Chequered
Red sided
Flame
Black neck
and many more...
NOTE: Garters are not constrictors.
Or you could go with a Rat snake(think corns come under rat snake,correct me if im wrong.) ,which are usually pretty docile,slow(when it suits them), and layed back creatures.They are constrictors of course which is also very interesting to watch whether you feed live or dead food
.They do of course grow a lot bigger and stronger than garters and can often exceed 5ft in length.
Quite a few different Rat snakes you can go for
Fox snake (looks a lot like a copperhead,you can look the other pics up your self , just happened to have a fox snake pic on the comp that I googled)
Black rat
Corn snake
and a heck of a lot more go here -
Rat snake - Wikipedia, the free encyclopedia
I have no idea if some of those are endangered but still, some of the more common ones are there too.
Both garters and rat snakes suitable for first buys
. When you finally descide make sure u show a big interest in caring for the snake and your parents will probably realise how much you are reading into it and will let you get something bigger next time.
Best of luck