I was broke for a long time, and then I changed how I powered up things.
Set a stardust goal, say 20K. Hit that goal, and then do one power-up. Raise the goal 5k, to 25K, and when you hit that, do another power-up. That invests 5K in savings for every power-up you do, balancing savings and powering up. Working great so far, I'm up from zero to 84K, working on hitting 90K so I can do another power-up for B/C Ttar for my Mewtwo raid on Saturday. (If I don't get it to 30, I'll finish the trip to 30, and then bump my requirements appropriately.)