The best replacement for gesso is primer.

The best alternatives to gesso are rated as following:
★★★★★  primer
★★★  white paint
★★★  mod podge
★★★  matte medium
★★★  gel medium
★★  modeling paste
★★  liquid white
★  chalk paint
★  modge podge
★  kilz
★  acrylic primer
★  traditional gesso
  molding paste
  titanium white

Your alternative for gesso is not listed? Suggest!
Speaking about gesso, one probably shouldn't forget about acrylic.

Other search terms related to gesso and their ratings are:
★★★★★ acrylic
★★★ distress
★★★ oil paint
★★ oil paints
★ oil pastels
You have in mind a companion for gesso and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gesso in all years. Click on graph for more.
gesso
primer
white paint