Welcome to Grey Goo's Supplies Corner

Everyone needs to start somewhere and I think starting here is a good plan.

1. Paint Brushes
This one should be a given and clearly if you want to paint models you will need some paint brushes. There are various types of brushes out there and some work best with different paint types like acrylic, oil and water colour. Lets break them down for you:
• Synthetic, such as nylon or polyester
These types of brushes will come in all sorts of prices and you can find them in dollar stores all the way up to professional art supply stores.
• Natural, such as Ox, Squirrel or Sable
Now these types of brushes can get expensive very quickly. Sable is generally considered the best hobby brush on the market. You will really only find these kind of brushes at specialty supplies stores.
My recommendation is that you start with synthetic brushes until you get comfortable with handling the brush, including properly cleaning them, before you move on to natural brushes. A single Sable brush can cost between $50-$100. I will buy large packs of synthetic brushes from the dollar store often and they work well enough for most tasks.
2. Paint
Now that you have your brushes its time to get some paint. Paints come in all kinds of mediums, colours, brands and sizes. You will have lots to choose from so lets have a look.
• Craft, brands like Apple Barrel and the like
These paints, while very cheap, come in large amounts, have low pigment values and are quite thick. They will have to be thinned to paint models and this can be hard to do. They can be great to use for baseing your models when you do not need to thin as much or when making larger items like scenery and large displays.
• Artist Acrylic, found in most traditional art supply stores, Windsor & Newton or Golden are some brands
These kind of paints can work well and often have medium to high pigment values. Often these brands can be limited in the colours they offer since the expectation is that you will mix your own colours. The price for these paints can be all over the place, from 10 tubes for a couple dollars to $100 for a single tube. You won't have any issues using these paints.
• Hobby Acrylic, found in most hobby stores and online
These paints will tend to be the "go to" for most hobby painters. They have high pigment values and thin well. They come in tons of colours so you don't have to mix your own, although you can if you like. The price of these paints is usually pretty stable at around $7 a bottle with bundles at a savings. The only real downside is they tend to be on the smaller size and if you plan on doing large displays, scenery, or large batch painting jobs you will either run out or need to buy lots of extra. I do not recommend these paints for that use.
• Oil paint, comes in both traditional and hobby styles
Oil paints can be lots of fun, but they can be hard to work with and need special cleaning supplies. I would wait to buy these paints until you are comfortable with acrylic paints. Oil will let you create some amazing effects. I tend to create my own colours by mixing which is easier to do thanks to the nature of oil paints. As I mentioned there are hobby brands of oils and they do come in a large variety of colours if you still don't like mixing paints. Abteilung 502 is a good hobby oil paint.
My recommendation is that you start with some hobby acrylic paints that you can pick up at the same time as any models you may be purchasing. Often the model box will have suggested colours to get similar effects as the artwork on the box. If not, try to stick to only a handful of colours. If you have the money getting a complete set from a company like Scale75 and Vallejo can work quite well too.
3. Tools
There are lots of different kinds of tools you can use. There are clippers, files, paint handles and more. I will give you some ideas on the main tools you should consider getting. This list is nowhere near everything and it is not absolute.
• Flat edge clippers
Flat edge clippers are used for removing your model pieces from the plastic sprew. There are many different kinds of clippers from different manufacters, durability and sharpness vary greatly from clipper to clipper. Games Workshop sells a really nice one but it can be too expensive for some. Your local hobby store can give you some other options.
• Brush pots
Brush pots are a great way to keep your brushes clean without damaging the tips. They usually have some way of holding the brush on the side of the cup. Not everyone uses specialty pots, instead just use a cup to hold some water. It's really up to you. Just be sure not to leave your brushes standing on the tips.
• Glues of various types such as hobby and white glue
You will have LOTS of glue choices and it is important that you use the right glue for the right job. You have hobby glues which usually are best used on plastics. These glues melt the plastic slightly to create a tight bond. Next you have superglues. These are good for glueing different materials such as metal to plastic. White glue or craft glue is great for attaching base details like rocks or fake grass. There are other types of glue on the market with a wide variety of prices.
• Files, such as nail or metal
When you are cleaning up your models for painting, you will often find mould lines or bits of sprew left on your models. This is where files and, in some cases, scrapers come in. Scrapers can get rid of mould lines and files can get rid of mold lines and bits of sprew. You just need to make sure you know how hard you can push. Some files and scrapers can be very strong and end up taking more of the model than you intended.
My recommendation is that you start with a good pair of clippers, a small metal file set, a bottle of white glue and some plastic glue such as Tamiya extra thin cement. As for brush pot, hobby stores usually stock some. If not, you can try Games Workshop, as they have some nice cups.