It all depends on what you want to accomplish. Model building can be as simple as gluing it together and throwing on some paint, and as complex as making large-scale models out of original materials. I once read a article on a gentleman who made a 1/8 scale Hurricane for a museum. The aluminum parts were aluminum, turned on a lathe. The tires were rubber, the seat belts were fabric and every rivet was duplicated in scale. Pretty amazing, and beyond anything I'd want to do.
Then there's this guy:
http://www.carrierbuilders.net/galle...prise_1-72.htm
Or this one:
http://www.kbismarck.com/models/graf-spee-terra.html
Most tools you won't even know exist until you need them.
My arsenal includes:
Airbrush and compressor. If you are a serious modeller these are vital tools. At your stage I would say they are expensive toys, something to worry about later.
Dremel Tool. This is a small drill designed specifically for modelling. It's made to work with plastic, and can make holes as small as .005". Again it's money you don't want to spend until you have to.
Pin Vise. This is a tiny drill that takes the same bits as the Dremel, but is powered by twirling your fingers. Cheap and effective, but slow.
Sandpaper, sanding blocks, sanding sticks. Handy for removing way-over-size rivets from older kits and for smoothing glue seams, which of course real planes don't have.
Pounce Wheel. Originally designed for tracing patterns from paper to fabric for sewing. The one day somebody figured out that if used on a plastic model it made perfect little indented rivets, barely noticable unless you look real hard. The holes will be completely filled by paint, so it's only worthwhile if you're also using an airbrush.
Rat-tailed file.
Super glue. For applying tiny parts, and parts made of different materials.
Gap-filling super glue. Handy for gluing parts end-on, such as metal struts.
Zip-Kicker. A spray accelerator that makes super glues dry almost instantly.
An assortment of paint brushes, from medium to ultra-tiny.
Proper paints. Olive Drab is nothing like British Dark Green, or French Green or Italian Green or Japanese Green. Getting the colors right can make a big difference. Olive drab in the 1940s is also nothing like the Olive Drab from the 1920s (commonly called Field Drab just to note the difference). Everybody has their own grey/gray, and they are easy to tell apart if you know what you're looking at.
So that's just the tip of the iceberg. The real tool, as always, is your brain. There are a lot more tips and tricks than there are tools, and the best way to learn is not to get too many tips at once, so I won't give you any. When you want to know how to do a particular thing, ask. There will always be somebody with an answer.