This page of the trophy guide to Marvel's Guardians of the Galaxy features a detailed description of the Galactic Frugality trophy. This trophy is obtained by paying the Nova Corps after the Guardians of the Galaxy were fined by them in the second chapter of the campaign.
This trophy is linked to several important choices made during the campaign. You can easily miss it and if that happens, you'll have to go through about half the game again to make different choices.
During chapter 2, you will be given the choice of whether to hide the llama or Rocket's equipment (screenshot no. 1). Depending on your choice, Ko-Rel will inform you that you need to pay a fine of either 7000 or 8000 credits (screenshot no. 2). This isn't a significant difference, since the Guardians will be able to earn much more credits in the future.
In chapter 3, you will have to make the important choice of selling Groot or Rocket.
The character you choose affects chapter 4, which starts with a meeting with Lady Hellbender:
- If you chose to sell Rocket, then after the battle, you will have to steal the credits from the treasury (screenshot no. 1). The game won't allow you to leave the area until you collect enough money to pay the fee.
- If you chose to sell Groot, then you will need to negotiate with Lady Hellbender (screenshot no. 2). It's best for Drax to take over, because that'll guarantee you the best deal.
Chapter 6, during which the team visits the market, is very important. In the course of this chapter, you need to avoid unnecessary expenses, i.e. don't let your money fall below 7000 or 8000 credits. If this happens, then immediately load the last checkpoint and make different choices.
You will only need to pay the fine in chapter 9. If you have at least 7000 or 8000 credits, then you can confirm the payment and you will get the achievement. If you don't have enough credits, you will miss the chance to unlock the trophy (during the given playthrough).