Mixing paints to create new colours is a useful skill for anyone who needs a small amount. Gold is both a basic colour and a metallic colour, which is difficult to duplicate. This will help you achieve the colour gold, not the metallic gold. Before you begin to randomly experiment, it's important to review the basic colour wheel. You can make all hues from the primary colours: red, yellow and blue. Orange, green and purple are secondary colours. From these you add white to achieve a tint of a colour or black to create a shade.
Measure a tbsp of yellow paint on a plate or in a plastic container. By keeping track of how much of each colour paint you add, you can duplicate the colour if you need a larger quantity.
Mix one tsp of each of the primary colours together on a plate: red, blue and yellow. This should give you a basic brown if you have an even amount of each colour.
Add a few drops of the brown paint to your yellow paint. Mix it to create a basic gold colour.
Add a drop of red to your gold paint if you want a gold shade that has more orange tinges. Add a drop of blue if you want a shade with green undertones.
Look at your colour in natural light. If you like the hue but want it lighter, add a drop of white paint. Likewise if you want it darker, add a drop of black.
If you are trying to tint an entire gallon of paint, it's best to let the paint store make the transition because they'll use universal tints to achieve the colour.
Creating a metallic gold will require mica powders and is very difficult to achieve without special training.