Can anybody give me any suitable equivalents for the phrase 'Give glad tidings' as in the example ' Give glad tidings to those who strive - they always get the best results.'
Tidings means news, or information. Glad tidings is happy news.
I'm not sure I'd use the phrase glad tidings in your example at all, to be honest. I wouldn't be giving good news to people who strive, but some kind of reward or praise.
So, for equivalents to give glad tidings I would offer:
Send good (or happy) news
For an equivalent to give glad tidings as it was used in your example I would offer:
Or, the ever popular:
Offer large sums of cash
Glad tidings would be used to wish someone a happy birthday or something of this nature.
An interesting way to get synonyms for that expression is to look for it in a book known to have many translations (here, the Bible) and then to work your way through said translations. Here, Isaiah 52:7 has (New International Version):
Other version include “bring good news of happiness”, “break the news that all's well”, “bring good news”, “bring good tidings of good” (King James; sounds weird), and “bring glad tidings of good things” (New King James).