You reach Passo del Cristallina (2438 m) by three routes:
1. From Lago del Naret (2310 m), over Passo del Naret (2438 m) - Capanna Cristallina (2349 m) - Passo del Cristallina. Cca 1 h 30 min.
2. Through Val Torta, by Capanna Cristallina (2349 m) to Passo del Cristallina.
3. From Robiei (1900 m) - Passo del Cristallina. Cca 2 h.
On the Swiss Hiking Scale, the ascent difficulty would be graded T3.
From Passo del Cristallina (2438 m) you approach the small glacier, lying below the northwestern slopes of Cristallina. You cross the glacier (no crevasses), follow the trails to the upper snow rests and scramble the last 100 m to the peak. If you choose well, you need not to climb, but take care because the mountain slope is very crumbly.
This is the easiest route on Cristallina, so in spring it's also very popular with tour skiers.
Good shoes, walking poles, if there's a lot of old snow on the slopes (not on glacier rests, which are flat), you would probably need also some winter equipment.