Photographing spores can be difficult, especially under oil immersion when they move continuously.
Various thickening agents can be used. Glycerine Jelly tends to make the spores collapse. Methyl Cellulose (aka wallpaper paste) is often used for similar purposes. Xantham Gum (on the "Free From" shelf at the supermarket), Alginate or Gelatine could also be tried.
Both methyl cellulose and xanthan gum contain structures that show up under contrast enhancement techniques (eg Phase Contrast, Differential Interference Contrast): bamboo ropes for methyl cellulose and minute granules for xanthan gum. (Either of these may vary with the source of the material).
Xanthan Gum can be prepared by adding the powder to water at about 1:5. Stir until all the white trapped air has disappeared. It keeps for at least a few weeks, but seal to keep out dust and prevent evaporation. To use touch the surface with a glass rod (or finger tip!) and touch onto the slide. As the coverslip is pressed down it will form a thin film without too many air bubbles.