Can I use white acrylic paint instead of gesso for the base of my oil painting?
I can tell you what I do. I don't gesso anything. I don't even think I own any gesso. Most of the stretched canvases you purchase today are already prepared with gesso and so are ready for painting. I like to use board rather than canvas. I personally don't care for the texture of canvas in my finished work. I purchase gesso board. This is masonite that has had gesso applied to one side. It comes in a variety of sizes from 4x4 inches to quite large. I generally work with smaller sizes: 4x4, 5x5, 6x6, 5x7, 8x10. You could purchase a piece of double faced masonite and cut it yourself then apply gesso if you wish. I'd rather buy it prepared. There are several different brands. The one I prefer is Ampersand and can be purchased from a number of on-line sources.
That said, you can paint oils over an acrylic base. I frequently do a value scale underpainting in Burnt Sienna and then appply my oils over that. Robert Warren actually base coats his canvases with orange acrylic and then does a value scale underpainting using black acrylic before applying oils. I have also used unprepared masonite. With this product I sand the surface to remove the shine and then apply two coats of bottled acrylic paint with a roller letting it dry between coats.
Many of the gessos you buy today are acrylic based. So, the short answer is yes, you can paint your canvas in whatever color acrylic paint you would like before applying your oils. There is no rule that says you have to start with a white surface, In fact, because most oils are translucent, the base color of the canvas can influence your finished piece in some wonderful ways. Gesso is a thicker product and if you are stretching your own canvases using unprepared canvas, then a couple of coats of gesso will give your canvas more body and seal the fabric so that it will accept paint properly. At the end of the day, for me it is too much trouble. I'd rather purchase my supports ready to paint. I'd rather paint than prepare surfaces.
Hope this helps.