Nothing about papier mache is really engraved in stone.

The basics:  paper and water.  Strips or pulp.

Most people add an adhesive.  150 years ago, they often used just moisture and pressure.

Gesso is a water-based sealer and surface preparation applied to a surface.  It used to be made from plaster, calcium carbonate or gypsum mixed with an adhesive.  The original adhesive was rabbit skin glue.  Unfortunately, rabbit skin glue absorbs moisture from the air, and swells when moist and shrinks when dry, causing cracks in the paint.  You can still buy/make/mix it, but the old problems with it still exist, and it's more expensive than modern gesso.

Modern gesso is acrylic.  It seals the PM so it doesn't soak up your paint.  If you apply several/many layers, it will also smooth out minor imperfections in your PM surface.  It doesn't absorb moisture nearly as much, as it is a type of plastic.  Acrylic gesso works very well with acrylic paints, commonly used on PM (but not exclusively).

PVA white craft glue is polyvinyl acetate, a similar type of plastic glue.  It also works well with acrylic gesso and acrylic paints. With other, older materials, you have to be careful what you combine, as some conflict with each other, like painting with watercolors on an oil-based surface.

You can add whatever you want to PM, but I usually stick with the very basics until I see a particular reason why I should add something else, usually as a solution to a certain problem.

Other types of adhesives can have their own problems. 

Hide glues can get brittle and crack.

Wheat flour, rice flour and potato flour (organic adhesives) have all been used for PM.  All of these will absorb moisture from the air, they will mold if they get damp and weren't sealed, and can attract vermin.  But they're cheap and easy to find.

Cellulose adhesive (also called methyl cellulose, or carbomethyl cellulose) is also organic, but it is made from highly processed wood pulp.  Once it dries, it won't absorb atmospheric moisture.  And since it's not food-based, it doesn't attract insects and rodents (or dogs).  It can be trickier to find, and is more expensive.  Cellulose wallpaper paste is one source.

Try not to get too involved with complicated recipes until you know why you're using them.  K.I.S.S. always seems to be good advice.

And have fun!

Sue

thanks for your replies- after youve primed your pm with your primers do you paint with plain acrylics? or do you mix your acrylic with your gesso or your own recipes too? sorry if youve included this in your answers already- it was sought of a lot to take in- some of the bowls ive seen in the gallery here have looked thick and very very shiny- i painted a bowl yesterday with plain acrylics and it looked awful compared really thin- and really matt