Sun remedies are kept on Sunday: chant Om Hram Hreem Hraum Sah Suryaya Namah, donate wheat, jaggery, and keep the weekday fast. Ruby is the graha's stone, but it should only be worn once Sun has been established as a functional benefic for your lagna.
Surya remedies are for authority, vitality and the relationship with the father — the parts of life the Sun signifies. They are prescribed when the Sun is weak or afflicted in a chart, not as a general tonic; a strong Sun needs no strengthening.
The corpus describes an ill-placed Sun as low self-esteem, absent energy and confidence, and friction with authority and with the father. That is the pattern these practices address.
The mantra, the weekday fast and the charity are safe for anyone — they address Sun without amplifying it. Ruby is not: a planetary gem strengthens whatever the graha is already doing, so it needs a chart reading first.
Sunday. Fasting, charity and mantra japa for Sun all belong to that day.
The classical Sankhya is 7,000 repetitions, completed over weeks rather than at once. Begin with one mala — 108 — a day and build up; sincerity matters more than arithmetic.
Ruby should be avoided by Capricorn, Aquarius lagna, where the graha is a functional malefic and the stone amplifies exactly what you were trying to correct. Every lagna not listed as recommended needs the chart read first.