Welcome, new guy.
Your ideal beginner locomotive depends on what you like, in terms of your interest in modelling in addition to other things. You have a choice of many different kinds of locomotives.
Engines that are suitable for beginners all tend to have some things in common. For one thing, they usually have boilers that are designed to run out fuel before they run out of water. They don't typically feature a way to replenish fuel and water while the engine is running.
They usually have simplified valve-gear, which is easy to operate, has relatively few parts and doesn't require much adjustment.
Another thing you might think about is how you would like the engine to look.Do you like engines that look like ones that run on British narrow-gauge lines? Or ones that look like they were built in the U.S.A.? Or some other country? There are lots of engines to choose from.
I can give you an example of a popular entry-level locomotive: the Accucraft Ruby. This is just one example of an entry-level engine.
http://www.accucraft.com/modelc/AC77-010-C.htm
This engine isn't a scale model of any particular "real" engine. You get that a lot in the live-steam hobby: little engines that "look like" full-size ones without being actual scale models. In the case of the "Ruby" engines, they look very similar to the light industrial or general purpose locomotives made by Baldwin in the U.S.A. The engine is very simple, with a butane burner in a single-flue boiler, and fixed-eccentric valve gear, which means it is reversed by swapping the steam inlet and outlet in the cyliders via a valve. It's about as easy to operate as you can get. There is no pressure gauge, because the safety valve protects the boiler from over-pressure, otherwise it's not really important to know the boiler pressure. If it runs, you've got enough pressure. It has no water gauge glass because it's designed to run out of fuel before it runs out of water. Then you wait for it to cool off a bit, refill the water and butane, and set it off again. It doesn't have radio control, and it has a very basic (but pleasing) level of detail.
Little "freelance" engines like this are a lot of fun, and can be equipped with lots of extras. For instance, a company called "Ozark Miniatures" offers a kit to build a wooden cab for these engines. You can do research and collect detail parts to make your engine look more like its full-sized counterpart, and you can build or buy all kinds of rolling stock for it to pull. Kit-built rolling stock tends to look nicer than factory-made.
Of course this is just one example. I picked the "Ruby" because you're American, but that is just an assumption on my part. Maybe you like British trains, or European ones. There are engines that are mechanically identical to the "Ruby" that look like engines from these countries too.
There is so much available, it's hard to recommend any one thing until you tell us more about what you like! Depending on your budget, you don't even need to start with an ultra-simple beginner style locomotive. Any butane-fired steam engine is pretty easy to operate. They can come with an amazing range of extra features and parts and controls and enhancements, but the basics are the same. Make sure there's water in it, and follow some basic safety rules and you will be able figure it out.
If you tell us more about what kind of steam trains you like, or what you picture in your mind when you imagine yourself running a small steam train, we can steer you towards your ideal model.