Caught a 100IV Ghastly from a research task - evolve and power up or wait for a hopeful community day when it could learn shadow claw?
I have plenty of candies and stardust.
Unless you have massive quantities of stardust (tens of millions) and absolutely nothing useful to spend it on the mean time, I'd advise against powering up a Gastly that you're not going to evolve right away. A powered up Gastly is no more useful than a Gastly that isn't powered up, which is to say not useful at all.
If you want to evolve it at some later point, you can always power it up then. In the meantime, the stardust you've got doesn't decrease in value, and you leave the option open of using it power up something that actually would be useful.
If you don’t need to use it hold out. I go plused a 100% ghastly and evolved it and leveled it up, before they started bring back legacy moves. Hex and shadow ball aren’t that bad, but after trading for a shadow claw Gengar it’s really strong. I am thinking they may make it so you just catch a Gengar for a research task with shadow claw. I’m hoping anyway lol