There's more to painting than just paint, brushes, and canvas. The following tools are useful for storage and cleanup:
Jars: Use glass jars with lids to hold your solvents and painting mediums. You need at least two: one for clean solvent that you use as a wetting solution, and one for dirty solvent that you use to dissolve paint from your brushes. You can use old recycled pickle jars (sized to hold about 1/2 to 1 cup), or get fancy with specially made jars with a wire spiral inside them. You can find them at most art suppliers. The wire helps you clean the paint solids from your brush. The jar must be glass solvent eats through some plastics, so use glass to be safe.
Pliers: Use this tool for hard-to-open tubes of paint.
Paint box: Use this box to store and transport your tools and paints. Some come with their own easel on the lid, which is handy to work from and to transport the painting. A plastic bin with a handle works nicely, too. Toolboxes sold at hardware stores are often more economical than a paint box sold at art supply stores. They just don't have all the fancy compartments.
Soap: You can use a bar of soap in a plastic container (as for traveling) to clean your brushes and hands. You can buy special soap for cleaning brushes that does a terrific job as well.
Aluminum foil: Use this everyday item when you can't clean your brushes right away. Wrap the brushes until you can clean them (always clean within an hour or so).