My artist's toolkit is fairly minimal as I tend to prefer to work with acrylic paint on canvas. My paint of choice is the Liquitex Heavy Body but I have incorporated a few Jane Davenport colours for the portraits...I'm really enjoying the tones and like the flatness of them, especially when working in altered books. Otherwise, the supplies I use are usually Liquitex as I've worked with them for years so I'm very familiar with them and they are easy for me to access where I live.
As far as gesso, I lean towards white but on occasion I love the way colours pop against the black. It's also fantastic when I work on altered books as I can black out any of the print if I want. The gloss medium & varnish are fantastic to use as a bonding agent (like glue), to make paints thinner and more transparent (I also add a bit of water) as well as finishing paintings. The heavy gel medium is something I also use with altered books as it bonds absolutely everything...it even works in a pinch around the house. And, the final product that I'm not the most comfortable with because it's in a spray can which isn't great for our environment but works really well to complete paintings is Krylon Spray Varnish. It leaves just a light protective sheen on the finished paintings which I prefer over a heavy coat of varnish.
Most of the time these products tend to be used on my altered books (except the varnishes) but I do occasionally like to use the different colours of gesso on a ground, which is particularly necessary when I stretch my own canvas.