You have some fairly fundmental decisions to make. Some basic questions might include:
Sail or power.
Surface or submarine.
Scale or functional.
If power then fast or slower eg . motor torpedo boat v cargo ship
Purchases as ready to run or work – sometimes a lot of work before you have a model to sail.
You also need to be honest about your skill levels, the tools that you have, the time that you are willing to spend and the amoun of money that you are willing to commit.
I agree with Richard, Ashley & Colin. Go & look at some models, identify what interests you and talk to the owners.