These are usually two separate effects:

• Dreamy glow / vintage blur: Often made with a soft-focus, mist, or diffusion filter on the lens, or added later in post-processing. A similar DIY version is to put the effect on a clear/UV filter rather than the lens itself.
• Sparkles: Usually called a starburst effect. This can also come from a dedicated filter or be added in software.
• Rainbow sparkle: Look for a diffraction grating filter.

DIY options mentioned by the community include smearing a little grease/Vaseline on a UV filter or breathing on it, but don’t apply anything directly to the lens. Directional smears can affect the direction of the streaks, and tapping/smudging changes the diffusion. Other experiment-friendly materials in front of the lens include plastic, cellophane, or partial obstructions.

A more extreme version comes from intentionally “detuned” or micro-scratched lenses, which can make highlights bloom, but that’s a specialist modification rather than a normal consumer technique.

Safest starting point: try a mist/diffusion filter for glow and a star filter for sparkles, or simulate both in post.