Paints/Inks and Additives
Paints - Oh boy is this a wide open topic there are so many lines of paints you can use but when starting out try to stick with acrylics. There quick dry time and ease of use makes them the best for starting out. As you advance you can start playing around with oils and all other kinds of additions to you paint box.
Paints made for hobby painting such as The Army painter Line, Vallejo, Citadel and others are a great place to start. You will have a wide selection of colors and enhancers too choose from. Sadly for some of us there is no local hobby store or any place that carries hobby supplies but there is a craft store and they carry craft paints. These paints are also a good place to start, but you are gonna have to work with them to get them thinned and some colors because of the size of the pigment can be grainy. Basically any acrylic paint short of house paint can be used you will just have to experiment as you go along.
Inks - (second Pic) Are the next step in your line up of paints that I like to tell people to get. Inks can be used for lining, washes, glazes, and a number of other uses. They provide a much more intense color so make sure you practice with them on something you can mess up on when first using them. All of the hobby paint lines carry them but I like to head to the local craft store for some of mine. They have a large selection of colors in both opaque and transparent.
Additives - There are all kinds of home brew and commercial additives that you can use to help your painting progress. These can be found in most of the hobby lines or in larger bottles at your local craft store. Now water will be your mainstay of additives and something I always use with my paints. I use distilled water that way I know that there will be no reaction with chemicals in the water supply (mine is heavy in iron). Besides water there are 3 main ones I recommend and a couple of sidebars I use.
Flo-Aid - will help your paints flow from the brush giving you a smoother finish
Slo-Dri - used to slow the drying time of your paints when doing wet blending
Glaze - used to give transparency to your paints for blending and highlighting
Gloss - used to give shine to a small portion of a mini if needed, think cockpits and lasers
Metallic - this will turn any color onto a metallic think a candy apple red marauder.
Now there are home brews for all of these but try them at your own risk I have found they do not work as well as the commercials.
I also recommended picking up a bunch of dropper bottles for washes you make and for storing smaller amounts of additives/paints instead of trying to use the big bottles.

