Not an expert by any means so please do take all my comments with a pinch of salt:
In my experience (I’m indian) it is common that coloured stones used in jewelry are not of particularly high quality even today. Rubies are particularly egregious, size and visual impact is prized over quality so stones used are heated/flux filled out the wazoo. Finding high quality rubies is a task and reauires I’m unsure if this would also have been the case in the 70s but as this was pre liberalisation stones from other countries would be even harder to procure, so I assume it would be. They look quite pinkish in the picture so my assumption - and take with a pinch of salt - is that the rubies are probably not worth much.
The gold content is likely to be reasonably high, of course pieces made in the 70s probably wouldn’t have even a gold mark on them but Indians in general tend to get pieces with high gold content (exceptions exist) so I would assume that 18k is likely. You could get this tested by a jeweler. I do however recall my mom and grandmom having some pieces where the metal used was not gold, however the stones were still diamond etc. (though this seems to be more common if the jewelry is in white metal rather than yellow) so if it turns out on the off chance the metal is not gold, that doesn’t mean the diamonds aren’t real.
As for the diamonds, I can’t tell in the picture if they’re old cuts or modern. A piece bought in the 70s could have MRBs in them. Again a jeweler probably can assist here (or more detailed pics could help the experts here).
All in all, I think this is quite a pretty set! I’m not sure how much you could get for it if you sell it, though. Once you have an idea of the quality and material cost you can see how to price it if you want to sell. I do feel like this may be a bit “ornate” for western audiences though. I feel like people in the West tend to be more toned down with their jewelry choices
Look more like pink sapphire to me. And if those aren’t rose cut diamonds I’d guess they might be sapphire too as the sparkle doesn’t look right for diamonds.