Kealii21,
Welcome to the forum.
There have been many posts here on this very subject if you do a search and you will find that there is really no agreement on the perfect airbrush as they are all pretty good and it boils down to personal tastes much like any tool.
I think most here would agree though that a double-action airbrush is your best bet as it will do anything you will ever need an airbrush to do.
The single-action models also have their place but it is better to just go to a double-action right off the bat and learn how to use it so that you don't start with a single-action now and find you have to buy another airbrush later to get a desired effect. There are basically two kinds of double-action airbrushes: gravity-feed with a built-in color cup on top, and siphon-feed which take both a metal color cup or plastic and glass bottle. Some people think that a gravity-feed is best to buy for modeling because they can spray at lower pressures, although I am not convinced of this unless you are talking about spraying at 3 or 4 psi which I think is silly. The design of the airbrush is basically another preference thing as some like the color cup on top as gravity-feed models are designed, and others like the color cup under the airbrush as the siphon-feed models are designed. Still others prefer the side-feed model which as the name implies, has the cup on the side allowing better visibility for intricate work like illustrators do with an airbrush. I have both gravity-feed airbrushes as well as siphon-feed models and I like them all. The gravity-feed models are a little bit faster to clean as there is no siphon-tube to clean, or plastic and glass jars to clean when finished as there are with siphon-feed models.
So it basically comes down to what style of airbrush you like and need.
If you plan on using the airbrush in a setting other than just modeling where more paint is needed such as T-shirt airbrushing, painting murals on walls, or other uses where 1-3 oz. of paint may be needed, then your choice is simple, get a siphon-feed model.
My personal choices for gravity feed airbrushes are the Badger Omni 4000, and Omni 5000. Iwata also makes good airbrushes such as the Eclipse CS and the Revolution CR. If you want a siphon-feed model then my choices are the Omni 3000, Badger Anthem 155, and Badger 150. Here again Iwata also has some excellent models in the Eclipse BCS, and Revolution BCR.
There are many very good models of siphon-feed airbrushes and others that are popular are the Badger Crescendo, and Paasche VL, both of which have a fatter body on the airbrush that some people prefer. I happen to prefer the slimmer design such as the Anthem 155 and Omni 3000.
The reasons I prefer Badger's products is because they are affordable, parts are readily available and no airbrush company takes care of their customers better than Badger.
That is why Badger sells twice as many airbrushes annually than all other airbrush manufacturers combined.
I hope this helps some.
Mike