Always remember that as long as you have some paints, brushes and canvas you can create a painting. Don’t ever let materials get in the way of your wish to express yourself on canvas. If you’re looking to implement the wet-on-wet oil technique you can not only buy it prepared, you can make it up with a good quality titanium white and add linseed oil to a similar consistency. This can then act as a foundation layer for ordinary oils to slide on top. You can add linseed oil or your mixed liquid white at any point to get oils moving. The same with acrylic, if you need a few layers because it’s not such good quality, apply it several times over (drying in-between). If you want it more watery to convey a watercolour effect, add lots of water. Everything is intermixable.
So the thing to ask yourself if you feel yourself being stopped by a lack in the materials is what have you got and go with that….. happy painting!