SneakyGremlins It isn’t all about high CP; you want high CP mixed with high IV, however getting both is rather hard! So it’s a balance.
If you have high CP but low IV (for me, anything under 90% is too low but YMMV), it’s not worth it, but equally, if you have a 98% Pokemon but it’s Level 7, you need to weigh up the stardust cost and whether it would be worth it.
There are actually very few Pokemon that are even worth bothering with, and even less that are worth powering up.
Pokemon you want high IVs for are:
• Tyrannitar (first form: Larvitar)
• Gyarados (first form: Magikarp)
• Dragonite (first form: Dratini)
• Machamp (first form: Machop)
• Salamence (first form: Bagon)
• Metagross (first form: Beldum)
• Aggron (first form: Aron)
• Snorlax
• Blissey (first form: Chansey)
• Rhydon (first form: Rhyhorn)
• Vaporeon (first form: Eevee)
• Slaking (first form: Slakoth) Slaking is debatable as to whether it’s worth powering up though as while its high CP is attractive, it’s fast move literally does nothing, so unless you know how to use Slaking correctly, it would be a waste to power up
As well as all Legendary Pokemon (note: Mew is a mythical Pokemon, not Legendary, and is not worth bothering with).
I would not evolve any of the above Pokemon that you’re struggling for candies for, as you’re a low level, so it’s advisable to wait until you’re much higher to attract higher CP and higher IVs.
The above Pokemon are the main ones that count. There are others that are specialist within their fields due to their type and movesets, but if you’re unsure, I wouldn’t waste your precious stardust.
I also definitely would absolutely not power anything up until you’re at least Level 25, though Level 30 would be better. While it’s tempting to, stardust is very rare!